Question

I want to do a simple color replace on a BufferedImage, in java.

Here is my code:

public BufferedImage convertEDEDEDtoRGB(BufferedImage bufferedImage, 
short nr, short ng, short nb){

    short[] r = new short[256];
    short[] g = new short[256];
    short[] b = new short[256];
    short[] a = new short[256]; //leave a the same

    for(short i=0; i<r.length; i++) {
        r[i]=i;
        g[i]=i;
        b[i]=i;
        a[i]=i;         
    }


    System.out.println("componentSize "+bufferedImage.getColorModel().getComponentSize());
    for(int i = 0; i<bufferedImage.getColorModel().getComponentSize().length; i++)
        System.out.println("rgb ("+i+") " +bufferedImage.getColorModel().getComponentSize(i) ); //gives 8 bits

    System.out.println("num Components "+bufferedImage.getColorModel().getNumColorComponents()); // gives 3
    r[237] = nr; 
    g[237] = ng; 
    b[237] = nb;


    short[][] ededed2rgb = new short[][]{r, g, b, a};
    ShortLookupTable t = new ShortLookupTable(0, ededed2rgb);
    LookupOp  ededed2rgbOp = new LookupOp(t, null);

    bufferedImage = ededed2rgbOp.filter(bufferedImage, null);
    return bufferedImage;
}

This yields the following error, and I just do not see what I am mising:

 Number of color/alpha components should be 4 but length of bits array is 2

at java.awt.image.ColorModel.<init>(ColorModel.java:318)
    at java.awt.image.ComponentColorModel.<init>(ComponentColorModel.java:256)
 at java.awt.image.LookupOp.createCompatibleDestImage(LookupOp.java:396)
    at java.awt.image.LookupOp.filter(LookupOp.java:136)
    at nl.sytematic.projects.myproj.server.custom.MyServlet.convertEDEDEDtoRGB(GenerateFlavourImageServlet.java:225)

I tried with

new short[][] { r,g,b}

but the same error pops up. Any thoughts? I am loading a .png image (with transparency) by the way.

Answer 1

I changed the filter call into ededed2rgbOb.filter(bufferedImage, bufferedImage) and the error is gone. Found this out by inspecting the code at link. Supplying a second parameter effectively bypasses the createCompatibleDestImage.