Is there a function to sum the rasters of two buffered images?

Question

I'm doing 2D filteing and want to do element by element addition on grayscale BufferedImages. Is there an existing function that will complete this for me or do i need to make one from scrach?

Is there some sort of matrix class that converts a raster to a matrix to simplyfy this problem?

Edit: here is the general gist of it

    BufferedImageOp opX = new ConvolveOp(new Kernel(3,3, kernelX));
    BufferedImageOp opY = new ConvolveOp(new Kernel(3,3, kernelY));
    BufferedImage filtImageX = opX.filter(sourceImage, null);
    BufferedImage filtImageY = opY.filter(sourceImage, null);
    BufferedImage outputImage = addBufferedImages(filtImageX, filtImageY);

Grayscale Conversion:

public void toGrayscale() { 
     BufferedImageOp op = new ColorConvertOp(ColorSpace.getInstance(ColorSpace.CS_GRAY), null); 
     sourceImage = op.filter(sourceImage, null); 
}

Answer 1

I am not familiar with any java libs that do that for you.

You can get pixel at [i,j] with: image.getRGB(i, j);

BufferedImage image = ...;
BufferedImage resultImage = ...

int rgb= image.getRGB(i, j);
resultImage.setRGB(i, j, rgb);

You can also convert a buffered image to a byte array [ https://stackoverflow.com/a/7388025/1007845 ].
See this thread: how to convert image to byte array in java? to get a WritableRaster

EDIT:

It seems that WritableRaster might be useful in this case: http://docs.oracle.com/javase/1.4.2/docs/api/java/awt/image/WritableRaster.html

WritableRaster raster = image.getRaster();

for(int h=0;h<height;h++) {
    for(int w=0;w<width;w++) {
        int colour = 127;
      raster.setSample(w,h,0,colour); 
   }
}

Answer 2

I don't know of a direct way to do this.

But i can suggest a slightly underhanded approach. First, take your two images, and combine them into a single image with two bands. I'm hazy on the details of how to do this. I suspect you will want to create a Raster with a BandedSampleModel, and then blit the contents of the other two images into its DataBuffer. Although it looks like you should be able to create a two-bank DataBuffer which uses the arrays of the source images' (one-banked) DataBuffers as banks, which would avoid copying.

Once you have a two-band image, simply apply a BandCombineOp which sums the bands. You will need to express the summation as a matrix, but that shouldn't be hard. I think it would be [1.0, 1.0],or [0.5, 0.5] if you want to rescale the result.