CODEWITHSUNDEEP
javapngbit-depth
Lee
Lee

Reputation: 21

How to generate the image with grayscale and different bitdepth in java?

I am trying to implement some java code that can help to adjust the PNG image based on some characteristics of PNG image: e.g. Color Allowed Interpretation Type Bit Depths

0 1,2,4,8,16 Each pixel is a grayscale sample.

From which I searched that if the color type is 0, I should implement the code based on the different bit depth: 1, 2, 4, 8, 16, for the grayscale.

I want to use the Graphic2D lib, so I think:

 if (img_bitDepth == 16) {
            type = BufferedImage.TYPE_USHORT_GRAY; // 11
          } else if (img_bitDepth == 8) {
            type = BufferedImage.TYPE_BYTE_GRAY; //10
          } else if (img_bitDepth == 4) {
            type = BufferedImage.TYPE_BYTE_BINARY;
          } else if (img_bitDepth == 2) {
            type = BufferedImage.TYPE_BYTE_BINARY;
          } else if (img_bitDepth == 1) {
            type = BufferedImage.TYPE_BYTE_BINARY;
          } else {
            //logger warning.
          }

     BufferedImage resizedImage = new BufferedImage (img_width, img_height, type);

      Graphics2D g = resizedImage.createGraphics();
      g.drawImage(originalImage, 0, 0, img_width, img_height, null);
      g.dispose();

But I don't know how to set the bit dipth for 2 and 4 with the image type "TYPE_BYTE_BINARY".

Any suggestion?

Upvotes: 2

Views: 833

Answers (1)

Lee
Lee

Reputation: 21

I try to use this way, it seems work.

 private static final IndexColorModel createGreyscaleModel(int bitDepth) {

    // Only support these bitDepth(1, 2, 4) for now: Set the size.
    int size = 0;
    if (bitDepth == 1 || bitDepth == 2 || bitDepth == 4) {
      size = (int) Math.pow(2, bitDepth);
    } else {
      //logger error
      return null;
    }

    // generate the rgb and set the greyscale color.
    byte[] r = new byte[size];
    byte[] g = new byte[size];
    byte[] b = new byte[size];

    // The size should be larger or equal to 2, so we firstly set the start and end pixel color.
    r[0] = g[0] = b[0] = 0;
    r[size-1] = g[size-1] = b[size-1] = (byte)255;

    for (int i=1; i<size-1; i++) {
       r[i] = g[i] = b[i] = (byte)((255/(size-1))*i);
    }
    return new IndexColorModel(bitDepth, size, r, g, b);
 }


 type = BufferedImage.TYPE_BYTE_BINARY;
            IndexColorModel cm = createGreyscaleModel(img_bitDepth);
            resizedImage = new BufferedImage (img_width, img_height, type, cm);

Thanks.

Upvotes: 0

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