Java - get pixel array from image

Question

I m looking for the fastest way to get pixel data  int the form int      from a BufferedImage  My goal is to be able to address pixel  x  y  from the image using int x  y   All the methods I have found do not do this  most of them return int  s

User · Answer

Here is another FastRGB implementation found here:

public class FastRGB {
    public int width;
    public int height;
    private boolean hasAlphaChannel;
    private int pixelLength;
    private byte[] pixels;

    FastRGB(BufferedImage image) {
        pixels = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();
        width = image.getWidth();
        height = image.getHeight();
        hasAlphaChannel = image.getAlphaRaster() != null;
        pixelLength = 3;
        if (hasAlphaChannel)
            pixelLength = 4;
    }

    short[] getRGB(int x, int y) {
        int pos = (y * pixelLength * width) + (x * pixelLength);
        short rgb[] = new short[4];
        if (hasAlphaChannel)
            rgb[3] = (short) (pixels[pos++] & 0xFF); // Alpha
        rgb[2] = (short) (pixels[pos++] & 0xFF); // Blue
        rgb[1] = (short) (pixels[pos++] & 0xFF); // Green
        rgb[0] = (short) (pixels[pos++] & 0xFF); // Red
        return rgb;
    }
}

What is this?

Reading an image pixel by pixel through BufferedImage's getRGB method is quite slow, this class is the solution for this.

The idea is that you construct the object by feeding it a BufferedImage instance, and it reads all the data at once and stores them in an array. Once you want to get pixels, you call getRGB

Dependencies

import java.awt.image.BufferedImage;
import java.awt.image.DataBufferByte;

Considerations

Although FastRGB makes reading pixels much faster, it could lead to high memory usage, as it simply stores a copy of the image. So if you have a 4MB BufferedImage in the memory, once you create the FastRGB instance, the memory usage would become 8MB. You can however, recycle the BufferedImage instance after you create the FastRGB.

Be careful to not fall into OutOfMemoryException when using it on devices such as Android phones, where RAM is a bottleneck

User · Answer

I was just playing around with this same subject  which is the fastest way to access the pixels  I currently know of two ways for doing this    Using BufferedImage s getRGB   method as described in  tskuzzy s answer  By accessing the pixels array directly using   byte   pixels     DataBufferByte  bufferedImage getRaster   getDataBuffer    getData       If you are working with large images and performance is an issue  the first method is absolutely not the way to go  The getRGB   method combines the alpha  red  green and blue values into one int and then returns the result  which in most cases you ll do the reverse to get these values back   The second method will return the red  green and blue values directly for each pixel  and if there is an alpha channel it will add the alpha value  Using this method is harder in terms of calculating indices  but is much faster than the first approach   In my application I was able to reduce the time of processing the pixels by more than 90  by just switching from the first approach to the second   Here is a comparison I ve setup to compare the two approaches   import java awt image BufferedImage  import java awt image DataBufferByte  import java io IOException  import javax imageio ImageIO   public class PerformanceTest       public static void main String   args  throws IOException          BufferedImage hugeImage   ImageIO read PerformanceTest class getResource  12000X12000 jpg            System out println  Testing convertTo2DUsingGetRGB           for  int i   0  i  lt  10  i               long startTime   System nanoTime             int     result   convertTo2DUsingGetRGB hugeImage            long endTime   System nanoTime             System out println String format   -2d   s    i   1   toString endTime - startTime                    System out println             System out println  Testing convertTo2DWithoutUsingGetRGB           for  int i   0  i  lt  10  i               long startTime   System nanoTime             int     result   convertTo2DWithoutUsingGetRGB hugeImage            long endTime   System nanoTime             System out println String format   -2d   s    i   1   toString endTime - startTime                      private static int     convertTo2DUsingGetRGB BufferedImage image          int width   image getWidth          int height   image getHeight          int     result   new int height  width          for  int row   0  row  lt  height  row               for  int col   0  col  lt  width  col                  result row  col    image getRGB col  row                             return result           private static int     convertTo2DWithoutUsingGetRGB BufferedImage image           final byte   pixels     DataBufferByte  image getRaster   getDataBuffer    getData          final int width   image getWidth          final int height   image getHeight          final boolean hasAlphaChannel   image getAlphaRaster      null         int     result   new int height  width         if  hasAlphaChannel             final int pixelLength   4           for  int pixel   0  row   0  col   0  pixel   3  lt  pixels length  pixel    pixelLength                int argb   0              argb       int  pixels pixel   amp  0xff   lt  lt  24      alpha             argb      int  pixels pixel   1   amp  0xff      blue             argb       int  pixels pixel   2   amp  0xff   lt  lt  8      green             argb       int  pixels pixel   3   amp  0xff   lt  lt  16      red             result row  col    argb              col                if  col    width                   col   0                 row                                     else            final int pixelLength   3           for  int pixel   0  row   0  col   0  pixel   2  lt  pixels length  pixel    pixelLength                int argb   0              argb    -16777216     255 alpha             argb      int  pixels pixel   amp  0xff      blue             argb       int  pixels pixel   1   amp  0xff   lt  lt  8      green             argb       int  pixels pixel   2   amp  0xff   lt  lt  16      red             result row  col    argb              col                if  col    width                   col   0                 row                                            return result           private static String toString long nanoSecs          int minutes       int   nanoSecs   60000000000 0         int seconds       int   nanoSecs   1000000000 0   -  minutes   60         int millisecs     int      nanoSecs   1000000000 0  -  seconds   minutes   60     1000           if  minutes    0  amp  amp  seconds    0           return millisecs    ms         else if  minutes    0  amp  amp  millisecs    0           return seconds    s         else if  seconds    0  amp  amp  millisecs    0           return minutes    min         else if  minutes    0           return seconds    s     millisecs    ms         else if  seconds    0           return minutes    min     millisecs    ms         else if  millisecs    0           return minutes    min     seconds    s          return minutes    min     seconds    s     millisecs    ms            Can you guess the output      Testing convertTo2DUsingGetRGB  1   16s 911ms 2   16s 730ms 3   16s 512ms 4   16s 476ms 5   16s 503ms 6   16s 683ms 7   16s 477ms 8   16s 373ms 9   16s 367ms 10  16s 446ms  Testing convertTo2DWithoutUsingGetRGB  1   1s 487ms 2   1s 940ms 3   1s 785ms 4   1s 848ms 5   1s 624ms 6   2s 13ms 7   1s 968ms 8   1s 864ms 9   1s 673ms 10  2s 86ms  BUILD SUCCESSFUL  total time  3 minutes 10 seconds

User · Answer

This worked for me   BufferedImage bufImgs   ImageIO read new File  c   adi bmp         double     data   new double      bufImgs getData   getPixels 0 0 bufImgs getWidth   bufImgs getHeight   data i

User · Answer

Something like this   int     pixels   new int w  h    for  int i   0  i  lt  w  i         for  int j   0  j  lt  h  j             pixels i  j    img getRGB  i  j

User · Answer

If useful  try this   BufferedImage imgBuffer   ImageIO read new File  c   image bmp      byte   pixels    byte   imgBuffer getRaster   getDataElements 0  0  imgBuffer getWidth    imgBuffer getHeight    null

User · Answer

I found Mota s answer gave me a 10 times speed increase - so thanks Mota   I ve wrapped up the code in a convenient class which takes the BufferedImage in the constructor and exposes an equivalent getRBG x y  method which makes it a drop in replacement for code using BufferedImage getRGB x y   import java awt image BufferedImage  import java awt image DataBufferByte   public class FastRGB        private int width      private int height      private boolean hasAlphaChannel      private int pixelLength      private byte   pixels       FastRGB BufferedImage image                 pixels     DataBufferByte  image getRaster   getDataBuffer    getData            width   image getWidth            height   image getHeight            hasAlphaChannel   image getAlphaRaster      null          pixelLength   3          if  hasAlphaChannel                        pixelLength   4                        int getRGB int x  int y                int pos    y   pixelLength   width     x   pixelLength            int argb   -16777216     255 alpha         if  hasAlphaChannel                        argb      int  pixels pos     amp  0xff   lt  lt  24      alpha                    argb      int  pixels pos     amp  0xff      blue         argb       int  pixels pos     amp  0xff   lt  lt  8      green         argb       int  pixels pos     amp  0xff   lt  lt  16      red         return argb

User · Answer

Mota s answer is great unless your BufferedImage came from a Monochrome Bitmap  A Monochrome Bitmap has only 2 possible values for its pixels  for example 0   black and 1   white   When a Monochrome Bitmap is used then the   final byte   pixels     DataBufferByte  image getRaster   getDataBuffer    getData      call returns the raw Pixel Array data in such a fashion that each byte contains more than one pixel   So when you use a Monochrome Bitmap image to create your BufferedImage object then this is the algorithm you want to use          This returns a true bitmap where each element in the grid is either a 0    or a 1  A 1 means the pixel is white and a 0 means the pixel is black         If the incoming image doesn t have any pixels in it then this method    returns null          param image     return     public static int     convertToArray BufferedImage image         if  image    null    image getWidth      0    image getHeight      0          return null          This returns bytes of data starting from the top left of the bitmap        image and goes down         Top to bottom  Left to right      final byte   pixels     DataBufferByte  image getRaster                getDataBuffer    getData         final int width   image getWidth        final int height   image getHeight         int     result   new int height  width        boolean done   false      boolean alreadyWentToNextByte   false      int byteIndex   0      int row   0      int col   0      int numBits   0      byte currentByte   pixels byteIndex       while   done                alreadyWentToNextByte   false           result row  col     currentByte  amp  0x80   gt  gt  7          currentByte    byte     int  currentByte   lt  lt  1           numBits             if   row    height - 1   amp  amp   col    width - 1                         done   true                    else                       col                 if  numBits    8                                currentByte   pixels   byteIndex                   numBits   0                  alreadyWentToNextByte   true                             if  col    width                                row                    col   0                   if   alreadyWentToNextByte                                        currentByte   pixels   byteIndex                       numBits   0                                                       return result

[java] Java - get pixel array from image

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