how to rotate a bitmap 90 degrees

Question

There is a statement in android canvas drawBitmap visiblePage  0  0  paint    When I add canvas rotate 90   there is no effect  But if I write   canvas rotate 90  canvas drawBitmap visiblePage  0  0  paint     I get no bitmap drawn  So what am I not doing right

User · Answer

Just be careful of Bitmap type from java platform call like from comm1x's and Gnzlt's answers, because it might return null. I think it is also more flexible if the parameter can be any Number and use infix for readability, depends on your coding style.

infix fun Bitmap.rotate(degrees: Number): Bitmap? {
    return Bitmap.createBitmap(
        this,
        0,
        0,
        width,
        height,
        Matrix().apply { postRotate(degrees.toFloat()) },
        true
    )
}

How to use?

bitmap rotate 90
// or
bitmap.rotate(90)

User · Answer

Short extension for Kotlin fun Bitmap rotate degrees  Float   Bitmap       val matrix   Matrix   apply   postRotate degrees        return Bitmap createBitmap this  0  0  width  height  matrix  true     And usage  val rotatedBitmap   bitmap rotate 90f

User · Answer

You can also try this one  Matrix matrix   new Matrix     matrix postRotate 90    Bitmap scaledBitmap   Bitmap createScaledBitmap bitmapOrg  width  height  true    Bitmap rotatedBitmap   Bitmap createBitmap scaledBitmap  0  0  scaledBitmap getWidth    scaledBitmap getHeight    matrix  true     Then you can use the rotated image to set in your imageview through  imageView setImageBitmap rotatedBitmap

User · Answer

Using Java createBitmap   method you can pass the degrees   Bitmap bInput   your input bitmap    bOutput  float degrees   45    rotation degree Matrix matrix   new Matrix    matrix setRotate degrees   bOutput   Bitmap createBitmap bInput  0  0  bInput getWidth    bInput getHeight    matrix  true

User · Answer

If you rotate bitmap  90 180 270 360 is ok but for other degrees canvas will draw bitmap with different size   So the best way is  canvas rotate degree rotateCenterPoint x rotateCenterPoint y     canvas drawBitmap       canvas rotate -degree rotateCenterPoint x rotateCenterPoint y    rotate back

User · Answer

In case your goal is to have a rotated image in an imageView or file you can use Exif to achieve that  The support library now offers that  https   android-developers googleblog com 2016 12 introducing-the-exifinterface-support-library html  Below is its usage but to achieve your goal you have to check the library api documentation for that  I just wanted to give a hint that rotating the bitmap isn t always the best way   Uri uri     the URI you ve received from the other app InputStream in  try     in   getContentResolver   openInputStream uri     ExifInterface exifInterface   new ExifInterface in        Now you can extract any Exif tag you want      Assuming the image is a JPEG or supported raw format   catch  IOException e         Handle any errors   finally     if  in    null        try         in close          catch  IOException ignored            int rotation   0  int orientation   exifInterface getAttributeInt      ExifInterface TAG ORIENTATION      ExifInterface ORIENTATION NORMAL   switch  orientation      case ExifInterface ORIENTATION ROTATE 90      rotation   90      break    case ExifInterface ORIENTATION ROTATE 180      rotation   180      break    case ExifInterface ORIENTATION ROTATE 270      rotation   270      break      dependency     compile  com android support exifinterface 25 1 0

User · Answer

public static Bitmap RotateBitmap Bitmap source  float angle          Matrix matrix   new Matrix          matrix postRotate angle         return Bitmap createBitmap source  0  0  source getWidth    source getHeight    matrix  true       To get Bitmap from resources   Bitmap source   BitmapFactory decodeResource this getResources    R drawable your img

User · Answer

Below is the code to rotate or re size your image in android  public class bitmaptest extends Activity        Override     public void onCreate Bundle icicle            super onCreate icicle           LinearLayout linLayout   new LinearLayout this               load the origial BitMap  500 x 500 px          Bitmap bitmapOrg   BitmapFactory decodeResource getResources                   R drawable android            int width   bitmapOrg width            int height   bitmapOrg height            int newWidth   200          int newHeight   200              calculate the scale - in this case   0 4f         float scaleWidth     float  newWidth    width          float scaleHeight     float  newHeight    height              createa matrix for the manipulation         Matrix matrix   new Matrix               resize the bit map         matrix postScale scaleWidth  scaleHeight              rotate the Bitmap         matrix postRotate 45               recreate the new Bitmap         Bitmap resizedBitmap   Bitmap createBitmap bitmapOrg  0  0                            width  height  matrix  true               make a Drawable from Bitmap to allow to set the BitMap            to the ImageView  ImageButton or what ever         BitmapDrawable bmd   new BitmapDrawable resizedBitmap            ImageView imageView   new ImageView this               set the Drawable on the ImageView         imageView setImageDrawable bmd               center the Image         imageView setScaleType ScaleType CENTER               add ImageView to the Layout         linLayout addView imageView                  new LinearLayout LayoutParams                        LayoutParams FILL PARENT  LayoutParams FILL PARENT                                          set LinearLayout as ContentView         setContentView linLayout             You can also check this link for details   http   www anddev org resize and rotate image - example-t621 html

User · Answer

I would simplify comm1x s Kotlin extension function even more    fun Bitmap rotate degrees  Float        Bitmap createBitmap this  0  0  width  height  Matrix   apply   postRotate degrees     true

User · Answer

By default the rotation point is the Canvas s  0 0  point  and my guess is that you may want to rotate it around the center   I did that   protected void renderImage Canvas canvas        Rect dest drawRect        drawRect   new Rect 0 0  mImage getWidth    mImage getHeight         dest   new Rect  int   canvas getWidth     2 - mImage getWidth     mImageResize   2      left                      int   canvas getHeight    2 - mImage getHeight    mImageResize   2      top                      int   canvas getWidth     2   mImage getWidth     mImageResize   2     right                      int   canvas getWidth     2   mImage getHeight    mImageResize   2      bottom      if  mRotate            canvas drawBitmap mImage  drawRect  dest  null         else           canvas save Canvas MATRIX SAVE FLAG     Saving the canvas and later restoring it so only this image will be rotated          canvas rotate 90 canvas getWidth     2  canvas getHeight    2           canvas drawBitmap mImage  drawRect  dest  null           canvas restore

[android] how to rotate a bitmap 90 degrees

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