如何在Java中创建新的灰度（BufferedImage.TYPE_BYTE_GRAY）图像？

Question

I want to create a grayscale image but problem is that how I can specify the value (0-255) for a pixel and read it during reading the same image.

     BufferedImage img = new BufferedImage(width, height , BufferedImage.TYPE_BYTE_GRAY);
            File file = null; 
            //create random image pixel by pixel
            for(int yHeight = 0; yHeight < height; yHeight++){ 
             for(int xWidth = 0; xWidth < width; xWidth++){ 
               img.setRGB(xWidth, yHeight, rgb);//here what values to specify 
               //for rgb (0-255)
                 }      
             }

//write image
             try{
               file = new File("D:\\Output.png");
               ImageIO.write(img, "png", file);

             }catch(IOException e){
               System.out.println("Error: " + e);
             }

and for reading the same image how can I get the same specified pixel value.

private static void marchThroughImage(BufferedImage image) {
        int w = image.getWidth();
        int h = image.getHeight();

        for (int i = 0; i < h; i++) {
          for (int j = 0; j < w; j++) {
            int pixel = image.getRGB(j, i);
           }
         }
      }

Answer 1

There are two different parts in your question:

• First to read / write an image in Java, you should use Java.imageio using this simple code

  BufferedImage image = javax.imageio.ImageIO.read(new File("path/to/the/image")) ; boolean written = javax.imageio.ImageIO.write(image, "png", new File("where/to/write/the/image")) ;

• Then to access / modify the pixels in your image, you should access the raster with getSample / setSample or if you need performance, you directly access the DataBuffer. Read my answer in this question: Efficient access to image pixels in Java