compare two images pixel by pixel in java programming

Question

hii to all I m doing a final year project on data extraction from an image for that purpose i want to know how, can I compare two images pixel by pixel in java can any body give me answer plz its important to me also code plz if possible

and i also want to extract data from image in editable form

Answer 1

If this is a school project, about the furthest I should take you is to tell you about the excellent Imagemagick library: JMagick. It won't take you too long to work through the documentation and discover how to do subtractive blending of images.

Answer 2

Store both images in a BufferedImage, and then use the method getRGB(int x, int y) this returns the RGB colors as in the pattern RRGGBB in hex code, you can get both RGBs of the same pixel in each image and compare.

Here is the code:

File file1 = new File("path/image1.jpg");
File file2 = new File("path/image2.jpg");

BufferedImage image1 = ImageIO.read(file1);
BufferedImage image2 = ImageIO.read(file2);

int columns = image1.getWidth();
int rows = image1.getHeight();

for (int row=0; row<rows; row++){
    for (int col=0; col<columns; col++){
       int rgb = image1.getRGB(col, row);
       int rgb2= image2.getRGB(col, row);
       //compare here
    }
 }

Answer 3

Medopal's answer will perform an approximate comparison for RGB images with no alpha chanel. The reason the comparison is approximate is because the RGB values are being "squashed" into a single integer, whereas the image colour resolution could be a lot higher than this.

To perform an exhaustive comparison you need to compare each image band separately:

BufferedImage image1 = ...
BufferedImage image2 = ...

Raster r1 = image1.getData();
Raster r2 = image2.getData();
boolean ret; // Stores result.

// Check image sizes and number of bands.  If there are different
// then no need to compare images as they are definitely not equal.
if (r1.getNumBands() != r2.getNumBands() ||
  r1.getWidth() != r2.getWidth() ||
  r1.getHeight() != r2.getHeight()) {
  ret = false;
} else {
  // #Bands and image bounds match so compare each sample in turn.

  ret = true;

  search:
  for (int i=0; i<r1.getNumBands(); ++i) {
    for (int x=0; x<r1.getWidth(); ++x) {
      for (int y=0; y<r1.getHeight(); ++y) {
        if (r1.getSample(x, y, i) != r2.getSample(x, y, i) {
          // At least one sample differs so result is false;
          ret = false;
          // Use labeled break to terminate all loops.
          break search;
        }
      }
    }
  }

  done:
}