使用从头创建的java将彩色图像转换为黑白图像

Question

I want to convert my picture from colored to Black and white which seems to be created from scratch. Here is the code which i tried as described on the different post:

    BufferedImage bi = ImageIO.read(new File("/Users/***/Documents/Photograph.jpg"));
    ColorConvertOp op = 
        new ColorConvertOp(ColorSpace.getInstance(ColorSpace.CS_GRAY), null);
    ImageIO.write(bi, "PNG", new File("/Users/bng/Documents/rendered2.png"));
    op.filter(bi, bi);

But still my image is not converted to the Black and white. Additionally, this code is increasing the rendered2.png image size to 10 folds. Also, it would be great if i could find some Java 8 way of doing this. Any suggestions?

Answer 1

Here is the code which worked for me:

    BufferedImage input = ImageIO.read(new File("/Users/bng/Documents/Photograph.jpg"));
    // Create a black-and-white image of the same size.
    BufferedImage im = new BufferedImage(input.getWidth(), input.getHeight(), BufferedImage.TYPE_BYTE_BINARY);
    // Get the graphics context for the black-and-white image.
    Graphics2D g2d = im.createGraphics();
    // Render the input image on it.
    g2d.drawImage(input, 0, 0, null);
    // Store the resulting image using the PNG format.
    ImageIO.write(im, "PNG", new File("/Users/bng/Documents/rendered.png"));

It was BufferedImage.TYPE_BYTE_BINARY which provided me the exact solution. Lokking for the Java 8 Version for above code.

Answer 2

1. You have to find RGB of the existing colors of the image you want to change it.

2. Fyi, you want to change it as white RGB value is (255,255,255) and for black RGB value is (0,0,0)

3. Following method easily do the color change if you apply correct way of your requirement

    private BufferedImage changeColor(BufferedImage image, int srcColor, int replaceColor) { BufferedImage destImage = new BufferedImage(image.getWidth(), image.getHeight(), BufferedImage.TYPE_INT_ARGB); Graphics2D g = destImage.createGraphics(); g.drawImage(image, null, 0, 0); g.dispose(); for (int width = 0; width < image.getWidth(); width++) { for (int height = 0; height < image.getHeight(); height++) { if (destImage.getRGB(width, height) == srcColor) { destImage.setRGB(width, height, replaceColor); } } } return destImage; } 

Answer 3

you have to use the ColorConvertOp in a proper way:

1. create Source image
2. apply filter
3. save dest

example:

BufferedImage src = ImageIO.read(new File("/Users/***/Documents/Photograph.jpg"));

ColorConvertOp op = 
    new ColorConvertOp(ColorSpace.getInstance(ColorSpace.CS_GRAY), null);
BufferedImage dest = op.filter(src, null);

ImageIO.write(dest, "PNG", new File("/Users/bng/Documents/rendered2.png"));

src:

dest: