Programmatically determine if 2 images will be the same using Java

Question

In JAVA, I am trying to programmatically determine if 2 images are equal when displayed on the screen (one AKA image, even if they have different color spaces Is there a piece of code that will return a boolean when displaying 2 images?

One example that I have is PNG PNG, which I converted to PNG with a gray scale. Both images look the same, and I would like to prove it programmatically. Another example is two images where they display the same color pixels on the screen, but the color used for 100% transparent pixels has changed.

Answer 1

I reviewed all the solutions and decided that they can tell you how different images were or work for some types of images, but not for all. Here is the solution I came up with ...

package image.utils; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Toolkit; import java.awt.color.ColorSpace; import java.awt.image.BufferedImage; import java.awt.image.ColorConvertOp; import java.awt.image.PixelGrabber; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import javax.imageio.ImageIO; import javax.imageio.ImageReader; import javax.imageio.stream.ImageInputStream; import javax.swing.ImageIcon; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * Utility methods used to interact with images. */ public class ImageUtils { private final static Logger logger = LoggerFactory.getLogger(ImageUtils.class); private static final boolean equals(final int[] data1, final int[] data2) { final int length = data1.length; if (length != data2.length) { logger.debug("File lengths are different."); return false; } for(int i = 0; i < length; i++) { if(data1[i] != data2[i]) { //If the alpha is 0 for both that means that the pixels are 100% //transparent and the color does not matter. Return false if //only 1 is 100% transparent. if((((data1[i] >> 24) & 0xff) == 0) && (((data2[i] >> 24) & 0xff) == 0)) { logger.debug("Both pixles at spot {} are different but 100% transparent.", Integer.valueOf(i)); } else { logger.debug("The pixel {} is different.", Integer.valueOf(i)); return false; } } } logger.debug("Both groups of pixels are the same."); return true; } private static final int[] getPixels(final BufferedImage img, final File file) { final int width = img.getWidth(); final int height = img.getHeight(); int[] pixelData = new int[width * height]; final Image pixelImg; if (img.getColorModel().getColorSpace() == ColorSpace.getInstance(ColorSpace.CS_sRGB)) { pixelImg = img; } else { pixelImg = new ColorConvertOp(ColorSpace.getInstance(ColorSpace.CS_sRGB), null).filter(img, null); } final PixelGrabber pg = new PixelGrabber(pixelImg, 0, 0, width, height, pixelData, 0, width); try { if(!pg.grabPixels()) { throw new RuntimeException(); } } catch (final InterruptedException ie) { throw new RuntimeException(file.getPath(), ie); } return pixelData; } /** * Gets the {@link BufferedImage} from the passed in {@link File}. * * @param file The <code>File</code> to use. * @return The resulting <code>BufferedImage</code> */ @SuppressWarnings("unused") final static BufferedImage getBufferedImage(final File file) { Image image; try (final FileInputStream inputStream = new FileInputStream(file)) { // ImageIO.read(file) is broken for some images so I went this // route image = Toolkit.getDefaultToolkit().createImage(file.getCanonicalPath()); //forces the image to be rendered new ImageIcon(image); } catch(final Exception e2) { throw new RuntimeException(file.getPath(), e2); } final BufferedImage converted = new BufferedImage(image.getWidth(null), image.getHeight(null), BufferedImage.TYPE_INT_ARGB); final Graphics2D g2d = converted.createGraphics(); g2d.drawImage(image, 0, 0, null); g2d.dispose(); return converted; } /** * Compares file1 to file2 to see if they are the same based on a visual * pixel by pixel comparison. This has issues with marking images different * when they are not. Works perfectly for all images. * * @param file1 First file to compare * @param file2 Second image to compare * @return <code>true</code> if they are equal, otherwise * <code>false</code>. */ private final static boolean visuallyCompareJava(final File file1, final File file2) { return equals(getPixels(getBufferedImage(file1), file1), getPixels(getBufferedImage(file2), file2)); } /** * Compares file1 to file2 to see if they are the same based on a visual * pixel by pixel comparison. This has issues with marking images different * when they are not. Works perfectly for all images. * * @param file1 Image 1 to compare * @param file2 Image 2 to compare * @return <code>true</code> if both images are visually the same. */ public final static boolean visuallyCompare(final File file1, final File file2) { logger.debug("Start comparing \"{}\" and \"{}\".", file1.getPath(), file2.getPath()); if(file1 == file2) { return true; } boolean answer = visuallyCompareJava(file1, file2); if(!answer) { logger.info("The files \"{}\" and \"{}\" are not pixel by pixel the same image. Manual comparison required.", file1.getPath(), file2.getPath()); } logger.debug("Finish comparing \"{}\" and \"{}\".", file1.getPath(), file2.getPath()); return answer; } /** * @param file The image to check * @return <code>true</code> if the image contains one or more pixels with * some percentage of transparency (Alpha) */ public final static boolean containsAlphaTransparency(final File file) { logger.debug("Start Alpha pixel check for {}.", file.getPath()); boolean answer = false; for(final int pixel : getPixels(getBufferedImage(file), file)) { //If the alpha is 0 for both that means that the pixels are 100% //transparent and the color does not matter. Return false if //only 1 is 100% transparent. if(((pixel >> 24) & 0xff) != 255) { logger.debug("The image contains Aplha Transparency."); return true; } } logger.debug("The image does not contain Aplha Transparency."); logger.debug("End Alpha pixel check for {}.", file.getPath()); return answer; } } 

Answer 2

For grayscale images, I used the Mean Square Error as an indicator of how two different images used to be. Just insert the corresponding pixels from each image into the formula.

Not only can this tell you if they are exactly the same, but it can also tell you how different the two images are, although quite rudely.

https://en.wikipedia.org/wiki/Mean_squared_error

EDIT:

Note. This is C # code, not Java (apologies, but what I wrote at the beginning), however it should be easily portable.

 //Calculates the MSE between two images private double MSE(Bitmap original, Bitmap enhanced) { Size imgSize = original.Size; double total = 0; for (int y = 0; y < imgSize.Height; y++) { for (int x = 0; x < imgSize.Width; x++) { total += System.Math.Pow(original.GetPixel(x, y).R - enhanced.GetPixel(x, y).R, 2); } } return (total / (imgSize.Width * imgSize.Height)); } 

Answer 3

If you mean the same thing, compare each pixel.

If you want to compare the RGB image and the grayscale image, you first need to convert RGB to grayscale, for this you need to know how you used to do RGB-> Greyscale, there are different ways to do this and you can get different results.

Change if the method used in RGB-> Greyscale is a liner, you can work out a, b, c in the formula grey = a*R + b*G + c*B by comparing 3 pixels.

Answer 4

One of the easiest approaches I've tried is to get a pixel array of both images and compare them with the Arrays.equals method. Code example:

 package image_processing; import java.awt.image.BufferedImage; import java.awt.image.DataBufferByte; import java.io.File; import java.io.IOException; import java.util.Arrays; import javax.imageio.ImageIO; public class CheckPixels { public static void main(String args[]) throws IOException { File pic1 = new File("D:\\ani\\img1.png"); File pic2 = new File("D:\\ani\\img2.png"); if (Arrays.equals(returnPixelVal(pic1), returnPixelVal(pic2))) { System.out.println("Match"); } else { System.out.println("No match"); } } public static byte[] returnPixelVal(File in) { BufferedImage img = null; File f = null; byte[] pixels = null; // read image try { f = in; img = ImageIO.read(f); pixels = ((DataBufferByte) img.getRaster().getDataBuffer()).getData(); } catch (IOException e) { System.out.println(e); } return pixels; } } 

Answer 5

You can try this

Example [Broken Link]

They explained how they compared the two images ...