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); 
}

score 1 · Accepted Answer · edited May 23 '17 at 10:34

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); 
   }
}

edited May 23 '17 at 10:34

Community

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answered Mar 12 '12 at 15:40

Adrian

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it says an interger is returned. How can you grab the apropriate pixel from that? (I know that an int is 4bytes each one represents a different channel) Remember i've converted the colorspace to grayscale...so how do i interpret the information then. – Adam Mar 12 '12 at 16:51
@Adam for greyscale you calculate luminescence sth like: L = .30*R + .59*G + .11*B. Point I'm trying to make is that you still have integers. Could you post your code, it would help :) – Adrian Mar 12 '12 at 17:30
@Adam don't you still have R,G,B values after your convolution? where is the code where you can't get colour of the pixel as int? – Adrian Mar 12 '12 at 18:56
@Adam I edited the post to include WritableRaster. Try it out! – Adrian Mar 13 '12 at 14:54

Tom Anderson · Answer 2 · 2012-03-12T18:15:09.653

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.

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

2 Answers2