Fast Bitmap Blur For Android SDK

Question

Currently in an Android application that I m developing I m looping through the pixels of an image to blur it   This takes about 30 seconds on a 640x480 image     While browsing apps in the Android Market I came across one that includes a blur feature and their blur is very fast  like 5 seconds  so they must be using a different method of blurring   Anyone know a faster way other than looping through the pixels

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I found that decreasing contrast  brightness and saturation a little makes blurred images more pretty so I combined various methods from stack overflow and made this Blur Class  which deals with blurring images  changing brightness  saturation  contrast and size of the blurred images  It can also convert images from drawable to bitmap and vice-versa

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This is a shot in the dark  but you might try shrinking the image and then enlarging it again  This can be done with Bitmap createScaledBitmap Bitmap src  int dstWidth  int dstHeight  boolean filter   Make sure and set the filter parameter to true  It ll run in native code so it might be faster

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EDIT  April 2014   This is a question answer page that still gets a lot of hits it seems  I know I m always getting upvotes for this post  But if you re reading this  you need to realize the answers posted here  both mine and the accepted answer  are out of date  If you want to implement efficient blur today  you should use RenderScript instead of the NDK or Java  RenderScript runs on Android 2 2   using the Android Support Library   so there s no reason not to use it   The old answer follows  but beware as it s outdated     For future   Googlers  here is an algorithm that I ported from Yahel s port of Quasimondo s algorithm  but using the NDK  It s based on Yahel s answer  of course  But this is running native C code  so it s faster  Much faster  Like  40 times faster   I find that using the NDK is how all image manipulation should be done on Android    it s somewhat annoying to implement at first  read a great tutorial on using JNI and the NDK here   but much better  and near real time for a lot of things   For reference  using Yahel s Java function  it took 10 seconds to blur my 480x532 pixels image with a blur radius of 10  But it took 250ms using the native C version  And I m pretty sure it can still be further optimized    I just did a dumb conversion of the java code  there s probably some manipulations that can be shortened  didn t want to spend too much time refactoring the whole thing    include  lt jni h gt   include  lt string h gt   include  lt math h gt   include  lt stdio h gt   include  lt android log h gt   include  lt android bitmap h gt    define LOG TAG  libbitmaputils   define LOGI         android log print ANDROID LOG INFO LOG TAG   VA ARGS     define LOGE         android log print ANDROID LOG ERROR LOG TAG   VA ARGS     typedef struct       uint8 t red      uint8 t green      uint8 t blue      uint8 t alpha    rgba   JNIEXPORT void JNICALL Java com insert your package ClassName functionToBlur JNIEnv  env  jobject obj  jobject bitmapIn  jobject bitmapOut  jint radius        LOGI  Blurring bitmap               Properties     AndroidBitmapInfo   infoIn      void                pixelsIn      AndroidBitmapInfo   infoOut      void                pixelsOut       int ret          Get image info     if   ret   AndroidBitmap getInfo env  bitmapIn   amp infoIn    lt  0     ret   AndroidBitmap getInfo env  bitmapOut   amp infoOut    lt  0            LOGE  AndroidBitmap getInfo   failed   error  d   ret           return                Check image     if  infoIn format    ANDROID BITMAP FORMAT RGBA 8888    infoOut format    ANDROID BITMAP FORMAT RGBA 8888            LOGE  Bitmap format is not RGBA 8888             LOGE     gt   d  d   infoIn format  infoOut format           return                Lock all images     if   ret   AndroidBitmap lockPixels env  bitmapIn   amp pixelsIn    lt  0     ret   AndroidBitmap lockPixels env  bitmapOut   amp pixelsOut    lt  0            LOGE  AndroidBitmap lockPixels   failed   error  d   ret              int h   infoIn height      int w   infoIn width       LOGI  Image size is   i  i   w  h        rgba  input    rgba   pixelsIn      rgba  output    rgba   pixelsOut       int wm   w - 1      int hm   h - 1      int wh   w   h      int whMax   max w  h       int div   radius   radius   1       int r wh       int g wh       int b wh       int rsum  gsum  bsum  x  y  i  yp  yi  yw      rgba p      int vmin whMax        int divsum    div   1   gt  gt  1      divsum    divsum      int dv 256   divsum       for  i   0  i  lt  256   divsum  i              dv i     i   divsum              yw   yi   0       int stack div  3       int stackpointer      int stackstart      int rbs      int ir      int ip      int r1   radius   1      int routsum  goutsum  boutsum      int rinsum  ginsum  binsum       for  y   0  y  lt  h  y              rinsum   ginsum   binsum   routsum   goutsum   boutsum   rsum   gsum   bsum   0          for  i   -radius  i  lt   radius  i                  p   input yi   min wm  max i  0                  ir   i   radius     same as sir              stack ir  0    p red              stack ir  1    p green              stack ir  2    p blue              rbs   r1 - abs i               rsum    stack ir  0    rbs              gsum    stack ir  1    rbs              bsum    stack ir  2    rbs              if  i  gt  0                    rinsum    stack ir  0                   ginsum    stack ir  1                   binsum    stack ir  2                 else                   routsum    stack ir  0                   goutsum    stack ir  1                   boutsum    stack ir  2                                   stackpointer   radius           for  x   0  x  lt  w  x                   r yi    dv rsum               g yi    dv gsum               b yi    dv bsum                rsum -  routsum              gsum -  goutsum              bsum -  boutsum               stackstart   stackpointer - radius   div              ir   stackstart   div     same as sir              routsum -  stack ir  0               goutsum -  stack ir  1               boutsum -  stack ir  2                if  y    0                    vmin x    min x   radius   1  wm                             p   input yw   vmin x                 stack ir  0    p red              stack ir  1    p green              stack ir  2    p blue               rinsum    stack ir  0               ginsum    stack ir  1               binsum    stack ir  2                rsum    rinsum              gsum    ginsum              bsum    binsum               stackpointer    stackpointer   1    div              ir    stackpointer    div     same as sir              routsum    stack ir  0               goutsum    stack ir  1               boutsum    stack ir  2                rinsum -  stack ir  0               ginsum -  stack ir  1               binsum -  stack ir  2                yi                      yw    w            for  x   0  x  lt  w  x              rinsum   ginsum   binsum   routsum   goutsum   boutsum   rsum   gsum   bsum   0          yp   -radius   w          for  i   -radius  i  lt   radius  i                  yi   max 0  yp    x               ir   i   radius     same as sir              stack ir  0    r yi               stack ir  1    g yi               stack ir  2    b yi                rbs   r1 - abs i                rsum    r yi    rbs              gsum    g yi    rbs              bsum    b yi    rbs               if  i  gt  0                    rinsum    stack ir  0                   ginsum    stack ir  1                   binsum    stack ir  2                 else                   routsum    stack ir  0                   goutsum    stack ir  1                   boutsum    stack ir  2                              if  i  lt  hm                    yp    w                                  yi   x          stackpointer   radius          for  y   0  y  lt  h  y                  output yi  red   dv rsum               output yi  green   dv gsum               output yi  blue   dv bsum                rsum -  routsum              gsum -  goutsum              bsum -  boutsum               stackstart   stackpointer - radius   div              ir   stackstart   div     same as sir              routsum -  stack ir  0               goutsum -  stack ir  1               boutsum -  stack ir  2                if  x    0  vmin y    min y   r1  hm    w              ip   x   vmin y                stack ir  0    r ip               stack ir  1    g ip               stack ir  2    b ip                rinsum    stack ir  0               ginsum    stack ir  1               binsum    stack ir  2                rsum    rinsum              gsum    ginsum              bsum    binsum               stackpointer    stackpointer   1    div              ir   stackpointer     same as sir              routsum    stack ir  0               goutsum    stack ir  1               boutsum    stack ir  2                rinsum -  stack ir  0               ginsum -  stack ir  1               binsum -  stack ir  2                yi    w                          Unlocks everything     AndroidBitmap unlockPixels env  bitmapIn       AndroidBitmap unlockPixels env  bitmapOut        LOGI   Bitmap blurred        int min int a  int b        return a  gt  b   b   a     int max int a  int b        return a  gt  b   a   b      Then use it like this  considering a class called com insert your package ClassName and a native function called functionToBlur  as the code above states       Create a copy Bitmap bitmapOut   bitmapIn copy Bitmap Config ARGB 8888  true      Blur the copy functionToBlur bitmapIn  bitmapOut    radius     It expects a RGB 8888 bitmap   To use a RGB 565 bitmap  either create a converted copy before passing the parameter  yuck   or change the function to use a new rgb565 type instead of rgba   typedef struct       uint16 t byte0    rgb565    The problem is that if you do that you can t read  red   green and  blue of the pixel anymore  you need to read the byte properly  duh  When I needed that before  I did this   r    pixels x  byte0  amp  0xF800   gt  gt  8  g    pixels x  byte0  amp  0x07E0   gt  gt  3  b    pixels x  byte0  amp  0x001F   lt  lt  3    But there s probably some less dumb way of doing it  I m not much of a low-level C coder  I m afraid

User · Answer

Here is a realtime blurring overlay using RenderScript  which seems to be fast enough   https   github com mmin18 RealtimeBlurView

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For future Googlers  here is an algorithm that I ported from Quasimondo  It s kind of a mix between a box blur and a gaussian blur  it s very pretty and quite fast too   Update for people encountering the ArrayIndexOutOfBoundsException problem    anthonycr in the comments provides this information        I found that by replacing Math abs with StrictMath abs or some other   abs implementation  the crash does not occur           Stack Blur v1 0 from    http   www quasimondo com StackBlurForCanvas StackBlurDemo html    Java Author  Mario Klingemann  lt mario at quasimondo com gt     http   incubator quasimondo com       created Feburary 29  2004    Android port   Yahel Bouaziz  lt yahel at kayenko com gt     http   www kayenko com    ported april 5th  2012       This is a compromise between Gaussian Blur and Box blur    It creates much better looking blurs than Box Blur  but is    7x faster than my Gaussian Blur implementation        I called it Stack Blur because this describes best how this    filter works internally  it creates a kind of moving stack    of colors whilst scanning through the image  Thereby it    just has to add one new block of color to the right side    of the stack and remove the leftmost color  The remaining    colors on the topmost layer of the stack are either added on    or reduced by one  depending on if they are on the right or    on the left side of the stack          If you are using this algorithm in your code please add    the following line     Stack Blur Algorithm by Mario Klingemann  lt mario quasimondo com gt       public Bitmap fastblur Bitmap sentBitmap  float scale  int radius         int width   Math round sentBitmap getWidth     scale       int height   Math round sentBitmap getHeight     scale       sentBitmap   Bitmap createScaledBitmap sentBitmap  width  height  false        Bitmap bitmap   sentBitmap copy sentBitmap getConfig    true        if  radius  lt  1            return  null              int w   bitmap getWidth        int h   bitmap getHeight         int   pix   new int w   h       Log e  pix   w         h         pix length       bitmap getPixels pix  0  w  0  0  w  h        int wm   w - 1      int hm   h - 1      int wh   w   h      int div   radius   radius   1       int r     new int wh       int g     new int wh       int b     new int wh       int rsum  gsum  bsum  x  y  i  p  yp  yi  yw      int vmin     new int Math max w  h         int divsum    div   1   gt  gt  1      divsum    divsum      int dv     new int 256   divsum       for  i   0  i  lt  256   divsum  i              dv i     i   divsum              yw   yi   0       int     stack   new int div  3       int stackpointer      int stackstart      int   sir      int rbs      int r1   radius   1      int routsum  goutsum  boutsum      int rinsum  ginsum  binsum       for  y   0  y  lt  h  y              rinsum   ginsum   binsum   routsum   goutsum   boutsum   rsum   gsum   bsum   0          for  i   -radius  i  lt   radius  i                  p   pix yi   Math min wm  Math max i  0                 sir   stack i   radius               sir 0     p  amp  0xff0000   gt  gt  16              sir 1     p  amp  0x00ff00   gt  gt  8              sir 2     p  amp  0x0000ff               rbs   r1 - Math abs i               rsum    sir 0    rbs              gsum    sir 1    rbs              bsum    sir 2    rbs              if  i  gt  0                    rinsum    sir 0                   ginsum    sir 1                   binsum    sir 2                 else                   routsum    sir 0                   goutsum    sir 1                   boutsum    sir 2                                   stackpointer   radius           for  x   0  x  lt  w  x                   r yi    dv rsum               g yi    dv gsum               b yi    dv bsum                rsum -  routsum              gsum -  goutsum              bsum -  boutsum               stackstart   stackpointer - radius   div              sir   stack stackstart   div                routsum -  sir 0               goutsum -  sir 1               boutsum -  sir 2                if  y    0                    vmin x    Math min x   radius   1  wm                             p   pix yw   vmin x                 sir 0     p  amp  0xff0000   gt  gt  16              sir 1     p  amp  0x00ff00   gt  gt  8              sir 2     p  amp  0x0000ff                rinsum    sir 0               ginsum    sir 1               binsum    sir 2                rsum    rinsum              gsum    ginsum              bsum    binsum               stackpointer    stackpointer   1    div              sir   stack  stackpointer    div                routsum    sir 0               goutsum    sir 1               boutsum    sir 2                rinsum -  sir 0               ginsum -  sir 1               binsum -  sir 2                yi                      yw    w            for  x   0  x  lt  w  x              rinsum   ginsum   binsum   routsum   goutsum   boutsum   rsum   gsum   bsum   0          yp   -radius   w          for  i   -radius  i  lt   radius  i                  yi   Math max 0  yp    x               sir   stack i   radius                sir 0    r yi               sir 1    g yi               sir 2    b yi                rbs   r1 - Math abs i                rsum    r yi    rbs              gsum    g yi    rbs              bsum    b yi    rbs               if  i  gt  0                    rinsum    sir 0                   ginsum    sir 1                   binsum    sir 2                 else                   routsum    sir 0                   goutsum    sir 1                   boutsum    sir 2                              if  i  lt  hm                    yp    w                                  yi   x          stackpointer   radius          for  y   0  y  lt  h  y                     Preserve alpha channel    0xff000000  amp  pix yi                pix yi      0xff000000  amp  pix yi        dv rsum   lt  lt  16       dv gsum   lt  lt  8     dv bsum                rsum -  routsum              gsum -  goutsum              bsum -  boutsum               stackstart   stackpointer - radius   div              sir   stack stackstart   div                routsum -  sir 0               goutsum -  sir 1               boutsum -  sir 2                if  x    0                    vmin y    Math min y   r1  hm    w                            p   x   vmin y                sir 0    r p               sir 1    g p               sir 2    b p                rinsum    sir 0               ginsum    sir 1               binsum    sir 2                rsum    rinsum              gsum    ginsum              bsum    binsum               stackpointer    stackpointer   1    div              sir   stack stackpointer                routsum    sir 0               goutsum    sir 1               boutsum    sir 2                rinsum -  sir 0               ginsum -  sir 1               binsum -  sir 2                yi    w                       Log e  pix   w         h         pix length       bitmap setPixels pix  0  w  0  0  w  h        return  bitmap

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You can now use ScriptIntrinsicBlur from the RenderScript library to blur quickly  Here is how to access the RenderScript API  The following is a class I made to blur Views and Bitmaps   public class BlurBuilder       private static final float BITMAP SCALE   0 4f      private static final float BLUR RADIUS   7 5f       public static Bitmap blur View v            return blur v getContext    getScreenshot v               public static Bitmap blur Context ctx  Bitmap image            int width   Math round image getWidth     BITMAP SCALE           int height   Math round image getHeight     BITMAP SCALE            Bitmap inputBitmap   Bitmap createScaledBitmap image  width  height  false           Bitmap outputBitmap   Bitmap createBitmap inputBitmap            RenderScript rs   RenderScript create ctx           ScriptIntrinsicBlur theIntrinsic   ScriptIntrinsicBlur create rs  Element U8 4 rs            Allocation tmpIn   Allocation createFromBitmap rs  inputBitmap           Allocation tmpOut   Allocation createFromBitmap rs  outputBitmap           theIntrinsic setRadius BLUR RADIUS           theIntrinsic setInput tmpIn           theIntrinsic forEach tmpOut           tmpOut copyTo outputBitmap            return outputBitmap             private static Bitmap getScreenshot View v            Bitmap b   Bitmap createBitmap v getWidth    v getHeight    Bitmap Config ARGB 8888           Canvas c   new Canvas b           v draw c           return b

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Nicolas POMEPUY advice  I think this link will be helpful  Blur effect for Android design  Sample project at github   TargetApi Build VERSION CODES JELLY BEAN MR1  private static Bitmap fastblur16 Bitmap source  int radius  Context ctx            Bitmap bitmap   source copy source getConfig    true           RenderScript rs   RenderScript create ctx       Allocation input   Allocation createFromBitmap rs  source  Allocation MipmapControl MIPMAP NONE  Allocation USAGE SCRIPT       Allocation output   Allocation createTyped rs  input getType         ScriptIntrinsicBlur script   ScriptIntrinsicBlur create rs  Element U8 4 rs        script setRadius radius       script setInput input       script forEach output       output copyTo bitmap       return bitmap

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This code is work perfect for me  Bitmap tempbg   BitmapFactory decodeResource getResources   R drawable b1     Load a background  Bitmap final Bitmap   BlurImage tempbg      SuppressLint  NewApi   Bitmap BlurImage  Bitmap input        try           RenderScript  rsScript   RenderScript create getApplicationContext         Allocation alloc   Allocation createFromBitmap rsScript  input        ScriptIntrinsicBlur blur   ScriptIntrinsicBlur create rsScript    Element U8 4 rsScript        blur setRadius 21       blur setInput alloc        Bitmap result   Bitmap createBitmap input getWidth    input getHeight    Bitmap Config ARGB 8888       Allocation outAlloc   Allocation createFromBitmap rsScript  result        blur forEach outAlloc       outAlloc copyTo result        rsScript destroy        return result            catch  Exception e               TODO  handle exception         return input

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We tried to implement RenderScript blur like mentioned above in different answers  We were limited to use the v8 RenderScript version and that caused us a lot of trouble    Samsung S3 crashed randomly whenever we tried to use the renderscript Other devices  across different APIs  randomly showed different color issues   I want to share our dirty Java-only version which is slow and should be done on a separate thread and  if possible  before usage and therefore persisted   private final Paint mPaint   new Paint     public Bitmap blur final String pathToBitmap        final BitmapFactory Options options   new BitmapFactory Options        final Bitmap normalOne   BitmapFactory decodeFile pathToBitmap  options       final Bitmap resultBitmap   Bitmap createBitmap options outWidth  options outHeight  Bitmap Config ARGB 8888       Canvas canvas   new Canvas resultBitmap       mPaint setAlpha 180       canvas drawBitmap normalOne  0  0  mPaint       int blurRadius   12      for  int row   -blurRadius  row  lt  blurRadius  row    2            for  int col   -blurRadius  col  lt  blurRadius  col    2                if  col   col   row   row  lt   blurRadius   blurRadius                    mPaint setAlpha  blurRadius   blurRadius      col   col   row   row    1    2                   canvas drawBitmap normalOne  row  col  mPaint                                     normalOne recycle        return resultBitmap      This solution is far from perfect but creates a reasonable blur effect based on the fact  that it draws highly transparent version of the same image on top of a barely transparent  sharp  version  The alpha depends on the distance to the origin   You can adjust some  magic numbers  to your needs  I just wanted to share that  solution  for everybody who has issues with the v8 support version of RenderScript

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This worked fine for me  How to Blur Images Efficiently with Android s RenderScript  public class BlurBuilder       private static final float BITMAP SCALE   0 4f      private static final float BLUR RADIUS   7 5f        SuppressLint  NewApi       public static Bitmap blur Context context  Bitmap image            int width   Math round image getWidth     BITMAP SCALE           int height   Math round image getHeight     BITMAP SCALE            Bitmap inputBitmap   Bitmap createScaledBitmap image  width  height              false           Bitmap outputBitmap   Bitmap createBitmap inputBitmap            RenderScript rs   RenderScript create context           ScriptIntrinsicBlur theIntrinsic   ScriptIntrinsicBlur create rs              Element U8 4 rs            Allocation tmpIn   Allocation createFromBitmap rs  inputBitmap           Allocation tmpOut   Allocation createFromBitmap rs  outputBitmap           theIntrinsic setRadius BLUR RADIUS           theIntrinsic setInput tmpIn           theIntrinsic forEach tmpOut           tmpOut copyTo outputBitmap            return outputBitmap

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This is for all people who need to increase the radius of ScriptIntrinsicBlur to obtain a harder gaussian blur   Instead of to put the radius more than 25  you can scale down the image and get the same result  I wrote a class called GaussianBlur  Below you can see how to use  and the whole class implementation   Usage   GaussianBlur gaussian   new GaussianBlur context   gaussian setMaxImageSize 60   gaussian setRadius 25     max  Bitmap output   gaussian render  lt your bitmap gt  true   Drawable d   new BitmapDrawable getResources   output     Class    public class GaussianBlur       private final int DEFAULT RADIUS   25      private final float DEFAULT MAX IMAGE SIZE   400       private Context context      private int radius      private float maxImageSize       public GaussianBlur Context context        this context   context      setRadius DEFAULT RADIUS       setMaxImageSize DEFAULT MAX IMAGE SIZE               public Bitmap render Bitmap bitmap  boolean scaleDown        RenderScript rs   RenderScript create context        if  scaleDown            bitmap   scaleDown bitmap              Bitmap output   Bitmap createBitmap bitmap getWidth    bitmap getHeight    Config ARGB 8888        Allocation inAlloc   Allocation createFromBitmap rs  bitmap  Allocation MipmapControl MIPMAP NONE  Allocation USAGE GRAPHICS TEXTURE       Allocation outAlloc   Allocation createFromBitmap rs  output        ScriptIntrinsicBlur script   ScriptIntrinsicBlur create rs  inAlloc getElement        Element U8 4 rs        script setRadius getRadius         script setInput inAlloc       script forEach outAlloc       outAlloc copyTo output        rs destroy         return output     public Bitmap scaleDown Bitmap input        float ratio   Math min  float  getMaxImageSize     input getWidth     float  getMaxImageSize     input getHeight         int width   Math round  float  ratio   input getWidth         int height   Math round  float  ratio   input getHeight          return Bitmap createScaledBitmap input  width  height  true      public int getRadius         return radius     public void setRadius int radius        this radius   radius     public float getMaxImageSize         return maxImageSize     public void setMaxImageSize float maxImageSize        this maxImageSize   maxImageSize

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Use Render Script as mentioned here http   blog neteril org blog 2013 08 12 blurring-images-on-android

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For those still having issues with Renderscript support library on x86 chipsets  please have a look at this post by the creator of the library  It looks like the fix he prepared didn t make it somehow to the Build Tools v20 0 0  so he provides the files to fix it manually and a brief explanation of how to do it   https   code google com p android issues detail can 2 amp start 0 amp num 100 amp q  amp colspec ID 20Type 20Status 20Owner 20Summary 20Stars amp groupby  amp sort  amp id 71347

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Android Blur Guide 2016  with Showcase Benchmark App and Source on Github  Also check out the Blur framework I m currently working on  Dali   After experimenting a lot I can now safely give you some solid recommendations that will make your life easier in Android when using the Android Framework   Load and Use a downscaled Bitmap  for very blurry images   Never use a the full size of a Bitmap  The bigger the image the more needs to be blurred and also the higher the blur radius needs to be and usually  the higher the blur radius the longer the algorithm takes   final BitmapFactory Options options   new BitmapFactory Options    options inSampleSize   8  Bitmap blurTemplate   BitmapFactory decodeResource getResources    R drawable myImage  options     This will load the bitmap with inSampleSize 8  so only 1 64 of the original image  Test what inSampleSize suits your needs  but keep it 2 n  2 4 8      to avoid degrading quality due to scaling  See Google doc for more   Another really big advantage is that bitmap loading will be really fast  In my early blur testing I figured that the longest time during the whole blur process was the image loading  So to load a 1920x1080 image from disk my Nexus 5 needed 500ms while the blurring only took another 250 ms or so   Use Renderscript  Renderscript provides ScriptIntrinsicBlur which is a Gaussian blur filter  It has good visual quality and is just the fastest you realistically get on Android  Google claims to be  typically 2-3x faster than a multithreaded C implementation and often 10x  faster than a Java implementation   Renderscript is really sophisticated  using the fastest processing device  GPU  ISP  etc    etc   and there is also the v8 support library for it making it compatible down to 2 2  Well at least in theory  through my own tests and reports from other devs it seems that it is not possible to use Renderscript blindly  since the hardware driver fragmentation seems to cause problems with some devices  even with higher sdk lvl  e g  I had troubles with the 4 1 Nexus S  so be careful and test on a lot of devices  Here s a simple example that will get you started     define this only once if blurring multiple times RenderScript rs   RenderScript create context            this will blur the bitmapOriginal with a radius of 8 and save it in bitmapOriginal final Allocation input   Allocation createFromBitmap rs  bitmapOriginal     use this constructor for best performance  because it uses USAGE SHARED mode which reuses memory final Allocation output   Allocation createTyped rs  input getType     final ScriptIntrinsicBlur script   ScriptIntrinsicBlur create rs  Element U8 4 rs    script setRadius 8f   script setInput input   script forEach output   output copyTo bitmapOriginal     When using the v8 support with Gradle  which is specifically recommended by Google  because they include the latest improvements   you only need to add 2 lines to your build script and use android support v8 renderscript with current build tools  updated syntax for android Gradle plugin v14    android               defaultConfig                       renderscriptTargetApi 19         renderscriptSupportModeEnabled true           Simple benchmark on a Nexus 5 - comparing RenderScript with different other java and Renderscript implementations    The average runtime per blur on different pic sizes   Megapixels per sec that can be blurred  Each value is the avg of 250 rounds  RS GAUSS FAST is ScriptIntrinsicBlur  and nearly always the fastest   others that start with RS  are mostly convolve implementations with simple kernels  The details of the algorithms can be found here  This is not purely blurring  since a good portion is garbage collection that is measured  This can be seen in this here  ScriptIntrinsicBlur on a 100x100 image with about 500 rounds     The spikes are gc   You can check for yourself  the benchmark app is in the playstore  BlurBenchmark  Reuses Bitmap wherever possible  if prio  performance   memory footprint   If you need multiple blurs for a live blur or similar and your memory allows it do not load the bitmap from drawables multiple times  but keep it  cached  in a member variable  In this case always try to use the same variables  to keep garbage collecting to a minimum   Also check out the new inBitmap option when loading from a file or drawable which will reuse the bitmap memory and save garbage collection time   For blending from sharp to blurry  The simple and naive method is just to use 2 ImageViews  one blurred  and alpha fade them  But if you want a more sophisticated look that smoothly fades from sharp to blurry  then check out Roman Nurik s post about how to do it like in his Muzei app   Basically he explains that he pre-blurs some frames with different blur extents and uses them as keyframes in an animation that looks really smooth

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I used this before    public static Bitmap myblur Bitmap image  Context context                final float BITMAP SCALE   0 4f              final float BLUR RADIUS   7 5f              int width   Math round image getWidth     BITMAP SCALE               int height   Math round image getHeight     BITMAP SCALE               Bitmap inputBitmap   Bitmap createScaledBitmap image  width  height  false               Bitmap outputBitmap   Bitmap createBitmap inputBitmap               RenderScript rs   RenderScript create context               ScriptIntrinsicBlur theIntrinsic   ScriptIntrinsicBlur create rs  Element U8 4 rs                Allocation tmpIn   Allocation createFromBitmap rs  inputBitmap               Allocation tmpOut   Allocation createFromBitmap rs  outputBitmap               theIntrinsic setRadius BLUR RADIUS               theIntrinsic setInput tmpIn               theIntrinsic forEach tmpOut               tmpOut copyTo outputBitmap               return outputBitmap

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For future Googlers who choose NDK approach - i find reliable mentioned stackblur algorithm  I found C   implementation which does not rely on SSE here - http   www antigrain com   code include agg blur h html stack blur rgba32 which contains some optimizations using static tables like   static unsigned short const stackblur mul 255          512 512 456 512 328 456 335 512 405 328 271 456 388 335 292 512      454 405 364 328 298 271 496 456 420 388 360 335 312 292 273 512      482 454 428 405 383 364 345 328 312 298 284 271 259 496 475 456      437 420 404 388 374 360 347 335 323 312 302 292 282 273 265 512      497 482 468 454 441 428 417 405 394 383 373 364 354 345 337 328      320 312 305 298 291 284 278 271 265 259 507 496 485 475 465 456      446 437 428 420 412 404 396 388 381 374 367 360 354 347 341 335      329 323 318 312 307 302 297 292 287 282 278 273 269 265 261 512      505 497 489 482 475 468 461 454 447 441 435 428 422 417 411 405      399 394 389 383 378 373 368 364 359 354 350 345 341 337 332 328      324 320 316 312 309 305 301 298 294 291 287 284 281 278 274 271      268 265 262 259 257 507 501 496 491 485 480 475 470 465 460 456      451 446 442 437 433 428 424 420 416 412 408 404 400 396 392 388      385 381 377 374 370 367 363 360 357 354 350 347 344 341 338 335      332 329 326 323 320 318 315 312 310 307 304 302 299 297 294 292      289 287 285 282 280 278 275 273 271 269 267 265 263 261 259     static unsigned char const stackblur shr 255          9  11  12  13  13  14  14  15  15  15  15  16  16  16  16  17      17  17  17  17  17  17  18  18  18  18  18  18  18  18  18  19      19  19  19  19  19  19  19  19  19  19  19  19  19  20  20  20      20  20  20  20  20  20  20  20  20  20  20  20  20  20  20  21      21  21  21  21  21  21  21  21  21  21  21  21  21  21  21  21      21  21  21  21  21  21  21  21  21  21  22  22  22  22  22  22      22  22  22  22  22  22  22  22  22  22  22  22  22  22  22  22      22  22  22  22  22  22  22  22  22  22  22  22  22  22  22  23      23  23  23  23  23  23  23  23  23  23  23  23  23  23  23  23      23  23  23  23  23  23  23  23  23  23  23  23  23  23  23  23      23  23  23  23  23  23  23  23  23  23  23  23  23  23  23  23      23  23  23  23  23  24  24  24  24  24  24  24  24  24  24  24      24  24  24  24  24  24  24  24  24  24  24  24  24  24  24  24      24  24  24  24  24  24  24  24  24  24  24  24  24  24  24  24      24  24  24  24  24  24  24  24  24  24  24  24  24  24  24  24      24  24  24  24  24  24  24  24  24  24  24  24  24  24  24       I made modification of stackblur algorithm for multi-core systems - it can be found here http   vitiy info stackblur-algorithm-multi-threaded-blur-for-cpp   As more and more devices have 4 cores - optimizations give 4x speed benefit

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Thanks  Yahel for the code   Posting the same method with alpha channel blurring support as it took me some time to make it work correctly so it may save someone s time          Stack Blur v1 0 from    http   www quasimondo com StackBlurForCanvas StackBlurDemo html    Java Author  Mario Klingemann  lt mario at quasimondo com gt     http   incubator quasimondo com     lt p  gt     created Feburary 29  2004    Android port   Yahel Bouaziz  lt yahel at kayenko com gt     http   www kayenko com    ported april 5th  2012     lt p  gt     This is a compromise between Gaussian Blur and Box blur    It creates much better looking blurs than Box Blur  but is    7x faster than my Gaussian Blur implementation      lt p  gt     I called it Stack Blur because this describes best how this    filter works internally  it creates a kind of moving stack    of colors whilst scanning through the image  Thereby it    just has to add one new block of color to the right side    of the stack and remove the leftmost color  The remaining    colors on the topmost layer of the stack are either added on    or reduced by one  depending on if they are on the right or    on the left side of the stack      lt p  gt     If you are using this algorithm in your code please add    the following line     Stack Blur Algorithm by Mario Klingemann  lt mario quasimondo com gt       public static Bitmap fastblur Bitmap sentBitmap  float scale  int radius         int width   Math round sentBitmap getWidth     scale       int height   Math round sentBitmap getHeight     scale       sentBitmap   Bitmap createScaledBitmap sentBitmap  width  height  false        Bitmap bitmap   sentBitmap copy sentBitmap getConfig    true        if  radius  lt  1            return  null              int w   bitmap getWidth        int h   bitmap getHeight         int   pix   new int w   h       Log e  pix   w         h         pix length       bitmap getPixels pix  0  w  0  0  w  h        int wm   w - 1      int hm   h - 1      int wh   w   h      int div   radius   radius   1       int r     new int wh       int g     new int wh       int b     new int wh       int a     new int wh       int rsum  gsum  bsum  asum  x  y  i  p  yp  yi  yw      int vmin     new int Math max w  h         int divsum    div   1   gt  gt  1      divsum    divsum      int dv     new int 256   divsum       for  i   0  i  lt  256   divsum  i              dv i     i   divsum              yw   yi   0       int     stack   new int div  4       int stackpointer      int stackstart      int   sir      int rbs      int r1   radius   1      int routsum  goutsum  boutsum  aoutsum      int rinsum  ginsum  binsum  ainsum       for  y   0  y  lt  h  y              rinsum   ginsum   binsum   ainsum   routsum   goutsum   boutsum   aoutsum   rsum   gsum   bsum   asum   0          for  i   -radius  i  lt   radius  i                  p   pix yi   Math min wm  Math max i  0                 sir   stack i   radius               sir 0     p  amp  0xff0000   gt  gt  16              sir 1     p  amp  0x00ff00   gt  gt  8              sir 2     p  amp  0x0000ff               sir 3    0xff  amp   p  gt  gt  24                rbs   r1 - Math abs i               rsum    sir 0    rbs              gsum    sir 1    rbs              bsum    sir 2    rbs              asum    sir 3    rbs              if  i  gt  0                    rinsum    sir 0                   ginsum    sir 1                   binsum    sir 2                   ainsum    sir 3                 else                   routsum    sir 0                   goutsum    sir 1                   boutsum    sir 2                   aoutsum    sir 3                                   stackpointer   radius           for  x   0  x  lt  w  x                   r yi    dv rsum               g yi    dv gsum               b yi    dv bsum               a yi    dv asum                rsum -  routsum              gsum -  goutsum              bsum -  boutsum              asum -  aoutsum               stackstart   stackpointer - radius   div              sir   stack stackstart   div                routsum -  sir 0               goutsum -  sir 1               boutsum -  sir 2               aoutsum -  sir 3                if  y    0                    vmin x    Math min x   radius   1  wm                             p   pix yw   vmin x                 sir 0     p  amp  0xff0000   gt  gt  16              sir 1     p  amp  0x00ff00   gt  gt  8              sir 2     p  amp  0x0000ff               sir 3    0xff  amp   p  gt  gt  24                rinsum    sir 0               ginsum    sir 1               binsum    sir 2               ainsum    sir 3                rsum    rinsum              gsum    ginsum              bsum    binsum              asum    ainsum               stackpointer    stackpointer   1    div              sir   stack  stackpointer    div                routsum    sir 0               goutsum    sir 1               boutsum    sir 2               aoutsum    sir 3                rinsum -  sir 0               ginsum -  sir 1               binsum -  sir 2               ainsum -  sir 3                yi                      yw    w            for  x   0  x  lt  w  x              rinsum   ginsum   binsum   ainsum   routsum   goutsum   boutsum   aoutsum   rsum   gsum   bsum   asum   0          yp   -radius   w          for  i   -radius  i  lt   radius  i                  yi   Math max 0  yp    x               sir   stack i   radius                sir 0    r yi               sir 1    g yi               sir 2    b yi               sir 3    a yi                rbs   r1 - Math abs i                rsum    r yi    rbs              gsum    g yi    rbs              bsum    b yi    rbs              asum    a yi    rbs               if  i  gt  0                    rinsum    sir 0                   ginsum    sir 1                   binsum    sir 2                   ainsum    sir 3                 else                   routsum    sir 0                   goutsum    sir 1                   boutsum    sir 2                   aoutsum    sir 3                              if  i  lt  hm                    yp    w                                  yi   x          stackpointer   radius          for  y   0  y  lt  h  y                  pix yi     dv asum   lt  lt  24     dv rsum   lt  lt  16     dv gsum   lt  lt  8    dv bsum                rsum -  routsum              gsum -  goutsum              bsum -  boutsum              asum -  aoutsum               stackstart   stackpointer - radius   div              sir   stack stackstart   div                routsum -  sir 0               goutsum -  sir 1               boutsum -  sir 2               aoutsum -  sir 3                if  x    0                    vmin y    Math min y   r1  hm    w                            p   x   vmin y                 sir 0    r p               sir 1    g p               sir 2    b p               sir 3    a p                rinsum    sir 0               ginsum    sir 1               binsum    sir 2               ainsum    sir 3                rsum    rinsum              gsum    ginsum              bsum    binsum              asum    ainsum               stackpointer    stackpointer   1    div              sir   stack stackpointer                routsum    sir 0               goutsum    sir 1               boutsum    sir 2               aoutsum    sir 3                rinsum -  sir 0               ginsum -  sir 1               binsum -  sir 2               ainsum -  sir 3                yi    w                       Log e  pix   w         h         pix length       bitmap setPixels pix  0  w  0  0  w  h        return  bitmap

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from Mario Viviani blog one can use this solution from 17 Android Version   https   plus google com  MarioViviani posts fhuzYkji9zz  or   https   gist github com Mariuxtheone 903c35b4927c0df18cf8

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On the i o 2019 the following solution was presented          Blurs the given Bitmap image     param bitmap Image to blur     param applicationContext Application context     return Blurred bitmap image      WorkerThread fun blurBitmap bitmap  Bitmap  applicationContext  Context   Bitmap       lateinit var rsContext  RenderScript     try               Create the output bitmap         val output   Bitmap createBitmap                  bitmap width  bitmap height  bitmap config              Blur the image         rsContext   RenderScript create applicationContext  RenderScript ContextType DEBUG          val inAlloc   Allocation createFromBitmap rsContext  bitmap          val outAlloc   Allocation createTyped rsContext  inAlloc type          val theIntrinsic   ScriptIntrinsicBlur create rsContext  Element U8 4 rsContext           theIntrinsic apply               setRadius 10f              theIntrinsic setInput inAlloc              theIntrinsic forEach outAlloc                    outAlloc copyTo output           return output       finally           rsContext finish

[java] Fast Bitmap Blur For Android SDK

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