How to create valid image from RGB pixel values using java

Question

I have a 2D array which contains the RGB values. I need to create a valid image from these pixel values and save it. I have given the 2D array below. I wanted to implement this part in my project, so please help me with this. Thank you.

         int[] pixels = new int[imageSize * 3];
         int k = 0;
         for(int i=0; i<height; i++)
         {
            for(int j=0; j<width; j++)
            {
                if(k<imageSize*3)
               {
                    pixels[k] = r[i][j];
                    pixels[k+1] = g[i][j];
                    pixels[k+2] = b[i][j];
                }
               k = k+3;
            }
         }

Viktor Nordling · Accepted Answer · 2020-03-09 14:45:39Z

8

You can build a BufferedImage of type BufferedImage.TYPE_INT_RGB. This type represents a color as an int where:

3rd byte (16-23) is red,
2nd byte (8-15) is green and
1st byte (7-0) is blue.

You can get the pixel RGB value as follows:

int rgb = red;
rgb = (rgb << 8) + green; 
rgb = (rgb << 8) + blue;

Example (Ideone full example code):

  BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); 

  for (int y = 0; y < height; y++) {
     for (int x = 0; x < width; x++) {
        int rgb = r[y][x];
        rgb = (rgb << 8) + g[y][x]; 
        rgb = (rgb << 8) + b[y][x];
        image.setRGB(x, y, rgb);
     }
  }

  File outputFile = new File("/output.bmp");
  ImageIO.write(image, "bmp", outputFile);

edited Mar 9, 2020 at 14:45

Viktor Nordling

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answered Feb 23, 2015 at 10:14

Tobías

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1 Comment

user3364490 Over a year ago

Thank you so much, i have seen similar answers along with a raster class along with your example, and I got confused as i am unaware of that class usage. But your answer is working even without raster class. Thanks a lot.

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