Question

I need a bit help with Java’s ImageIO API. I seem to be lost in ComponentColorModel class. I need to check *.png file pixel by pixel to detect, whether it’s greyscale or color image. However, I can’t figure out how to obtain R, G, B values for each pixel. Can anyone help?

Following code throws IllegalArgumentException as it step on line “m.getComponents(i, components, 0);”

ComponentColorModel m = (ComponentColorModel) imageTypeSpecifier.getColorModel();
   int pixels = reader.getWidth(0) * reader.getHeight(0);
   isGray = true;

   int[] components = new int[4];
   for (int i = 0; i < pixels; i++) {
      m.getComponents(i, components, 0);
      if (!(components[0] != components[1] || components[1] != components[2])) {
         isGray = false;
         break;
      }
   }

Answer 1

My own solution:

BufferedImage buffImage = reader.read(0);
WritableRaster raster = buffImage.getRaster();
int[] colorsInPixel = new int[4];
isColor = false;

// check all pixels one by one
for (int i = 0; i < reader.getWidth(0) * reader.getHeight(0); i++) {
   raster.getPixel(i % reader.getWidth(0), i / reader.getHeight(0), colorsInPixel);
   if (colorsInPixel[0] != colorsInPixel[1] || colorsInPixel[1] != colorsInPixel[2]) {
      isColor = true;
   }
}