Member Avatar for takercena 
for(int x = 0; x < w; x++)
        {
            for(int y = 0; y < h; y++)
            {
              int rgb = bimg.getRGB(x,y);
              //byte r = (byte) ((rgb & 0x00ff0000) >> 16);
              //byte g = (byte) ((rgb & 0x0000ff00) >> 8);
              //byte b = (byte) (rgb & 0x000000ff);
              pixels[x][y] = ((int) rgb) & 0xff;
            }
        }
      
     
        
        processImage();
        for(int x = 0; x < w; x++)
        {
            for(int y = 0; y < h; y++)
            {
              int rgb = (pixels[x][y] | 0xff);
              bimg.setRGB(x, y, rgb);
              //byte r = (byte) ((rgb & 0x00ff0000) >> 16);
              //byte g = (byte) ((rgb & 0x0000ff00) >> 8);
              //byte b = (byte) (rgb & 0x000000ff);
            }
        }

I am learning how to process image in java. I want to know if the codes above are correct in processing grayscale jpeg image?

  • 3 Contributors
  • 5 Replies
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  • 2 Days Discussion Span
  • Latest Post Latest Post by masijade

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Member Avatar for masijade

Simply create a BufferedImage of the right size of type "BYTE_GRAY" and draw the colored image into it by retreiving the Graphics from the new BufferedImage and using drawImage with the coloredImage as the argument.

Member Avatar for takercena 
//Retrieve Image
        BufferedImage bimg = ImageIO.read( new File( "c:\\lena512.jpg" ) );
        bimg = bimg.getSubimage(0, 0, 512, 512);

        //Access it's pixel
        int w =  bimg.getWidth(null);
        int h =  bimg.getHeight(null);
        pixels = new int[w][h];
        for(int x = 0; x < w; x++)
        {
            for(int y = 0; y < h; y++)
            {
              int rgb = bimg.getRGB(x,y);
              byte r = (byte) ((rgb & 0x00ff0000) >> 16);
              byte g = (byte) ((rgb & 0x0000ff00) >> 8);
              byte b = (byte) (rgb & 0x000000ff);
              pixels[x][y] = (int)Math.round( 0.299 * r + 0.587 * g + 0.114 * b);
            }
        }
      
     
        
        processImage();

        for(int x = 0; x < w; x++)
        {
            for(int y = 0; y < h; y++)
            {
              int rgb = (pixels[x][y]);
              bimg.setRGB(x, y, rgb);
              //byte r = (byte) ((rgb & 0x00ff0000) >> 16);
              //byte g = (byte) ((rgb & 0x0000ff00) >> 8);
              //byte b = (byte) (rgb & 0x000000ff);
            }
        }
            //Draw back
            // Save as JPEG
            File file = new File("c:\\newimage.jpg");
            ImageIO.write(bimg, "jpg", file);       
    }

I am so sorry sir, but I can't get you. This is my full codes. The initial image is gray scale and I want to output back to newimage.jpg.

Edited by takercena because: n/a
Member Avatar for masijade

See the second part here.

P.S. Did you even try looking at the API docs, or finding tutorials for the classes listed in my post? No, you didn't, did you?

Edit: Also, you find the above tutorial with a simple Google search for Java grayscale as a link within the first result.

Edited by masijade because: n/a
Member Avatar for sorab

to convert an image (any type)to grey scale you can use the function :
ColorConvertOp colorConvert = new ColorConvertOp(ColorSpace.getInstance(ColorSpace.CS_GRAY), null);
colorConvert.filter(image, image);

Member Avatar for masijade

You should probably look at that link, too, BTW.

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