converting Java bitmap to byte array

Question

Bitmap bmp     intent getExtras   get  data      int size       bmp getRowBytes     bmp getHeight      ByteBuffer b   ByteBuffer allocate size      bmp copyPixelsToBuffer b      byte   bytes   new byte size      try        b get bytes  0  bytes length       catch  BufferUnderflowException e            always happens          do something with byte     When I look at the buffer after the call to copyPixelsToBuffer the bytes are all 0    The bitmap returned from the camera is immutable    but that shouldn t matter since it s doing a copy    What could be wrong with this code

User · Answer

Ted Hopp is correct  from the API Documentation    public void copyPixelsToBuffer  Buffer dst         After this method returns  the current position of the buffer is updated  the position is incremented by the number of elements written in the buffer     and  public ByteBuffer get  byte   dst  int dstOffset  int byteCount     Reads bytes from the current position into the specified byte array  starting at the specified offset  and increases the position by the number of bytes read

User · Answer

Try this to convert String-Bitmap or Bitmap-String          param bitmap     return converting bitmap and return a string     public static String BitMapToString Bitmap bitmap       ByteArrayOutputStream baos new ByteArrayOutputStream        bitmap compress Bitmap CompressFormat PNG 100  baos       byte    b baos toByteArray        String temp Base64 encodeToString b  Base64 DEFAULT       return temp             param encodedString     return bitmap  from given string      public static Bitmap StringToBitMap String encodedString       try          byte    encodeByte Base64 decode encodedString Base64 DEFAULT           Bitmap bitmap  BitmapFactory decodeByteArray encodeByte  0  encodeByte length           return bitmap       catch Exception e           e getMessage            return null

User · Answer

CompressFormat is too slow     Try ByteBuffer      Bitmap to byte     width   bitmap getWidth    height   bitmap getHeight     int size   bitmap getRowBytes     bitmap getHeight    ByteBuffer byteBuffer   ByteBuffer allocate size   bitmap copyPixelsToBuffer byteBuffer   byteArray   byteBuffer array         byte to bitmap     Bitmap Config configBmp   Bitmap Config valueOf bitmap getConfig   name     Bitmap bitmap tmp   Bitmap createBitmap width  height  configBmp   ByteBuffer buffer   ByteBuffer wrap byteArray   bitmap tmp copyPixelsFromBuffer buffer

User · Answer

Here is bitmap extension  convertToByteArray wrote in Kotlin            Convert bitmap to byte array using ByteBuffer      fun Bitmap convertToByteArray    ByteArray         minimum number of bytes that can be used to store this bitmap s pixels     val size   this byteCount        allocate new instances which will hold bitmap     val buffer   ByteBuffer allocate size      val bytes   ByteArray size         copy the bitmap s pixels into the specified buffer     this copyPixelsToBuffer buffer         rewinds buffer  buffer position is set to zero and the mark is discarded      buffer rewind          transfer bytes from buffer into the given destination array     buffer get bytes         return bitmap s pixels     return bytes

User · Answer

Try something like this   Bitmap bmp   intent getExtras   get  data    ByteArrayOutputStream stream   new ByteArrayOutputStream    bmp compress Bitmap CompressFormat PNG  100  stream   byte   byteArray   stream toByteArray    bmp recycle

User · Answer

Do you need to rewind the buffer  perhaps   Also  this might happen if the stride  in bytes  of the bitmap is greater than the row length in pixels   bytes pixel  Make the length of bytes b remaining   instead of size

User · Answer

In order to avoid OutOfMemory error for bigger files  I would solve the task by splitting a bitmap into several parts and merging their parts  bytes   private byte   getBitmapBytes Bitmap bitmap        int chunkNumbers   10      int bitmapSize   bitmap getRowBytes     bitmap getHeight        byte   imageBytes   new byte bitmapSize       int rows  cols      int chunkHeight  chunkWidth      rows   cols    int  Math sqrt chunkNumbers       chunkHeight   bitmap getHeight     rows      chunkWidth   bitmap getWidth     cols       int yCoord   0      int bitmapsSizes   0       for  int x   0  x  lt  rows  x                  int xCoord   0          for  int y   0  y  lt  cols  y                          Bitmap bitmapChunk   Bitmap createBitmap bitmap  xCoord  yCoord  chunkWidth  chunkHeight               byte   bitmapArray   getBytesFromBitmapChunk bitmapChunk               System arraycopy bitmapArray  0  imageBytes  bitmapsSizes  bitmapArray length               bitmapsSizes   bitmapsSizes   bitmapArray length              xCoord    chunkWidth               bitmapChunk recycle                bitmapChunk   null                    yCoord    chunkHeight             return imageBytes      private byte   getBytesFromBitmapChunk Bitmap bitmap        int bitmapSize   bitmap getRowBytes     bitmap getHeight        ByteBuffer byteBuffer   ByteBuffer allocate bitmapSize       bitmap copyPixelsToBuffer byteBuffer       byteBuffer rewind        return byteBuffer array

User · Answer

Your byte array is too small   Each pixel takes up 4 bytes  not just 1  so multiply your size   4 so that the array is big enough

User · Answer

Use below functions to encode bitmap into byte   and vice versa  public static String encodeTobase64 Bitmap image        Bitmap immagex   image      ByteArrayOutputStream baos   new ByteArrayOutputStream        immagex compress Bitmap CompressFormat PNG  90  baos       byte   b   baos toByteArray        String imageEncoded   Base64 encodeToString b  Base64 DEFAULT       return imageEncoded     public static Bitmap decodeBase64 String input        byte   decodedByte   Base64 decode input  0       return BitmapFactory decodeByteArray decodedByte  0  decodedByte length

[java] converting Java bitmap to byte array

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