将图像转换为黑白(不是灰度)

Question

你好我将图像从彩色转换为纯黑色和白色,结果是一个黑暗的图像.我没理由.以下是我的代码,它受到SO上其他代码的启发.任何指导都会有所帮助.

BufferedImage coloredImage = ImageIO.read(new File("/home/discusit/ninja.png"));
BufferedImage blackNWhite = new BufferedImage(coloredImage.getWidth(),coloredImage.getHeight(),BufferedImage.TYPE_BYTE_BINARY);
Graphics2D graphics = blackNWhite.createGraphics();
graphics.drawImage(blackNWhite, 0, 0, null);

我没有得到我做错的事.使用任何其他开源库的任何更多想法都可以.

工作:::::

BufferedImage coloredImage = ImageIO.read(new File("/home/abc/ninja.png"));
BufferedImage blackNWhite = new BufferedImage(coloredImage.getWidth(),coloredImage.getHeight(),BufferedImage.TYPE_BYTE_BINARY);
Graphics2D graphics = blackNWhite.createGraphics();
graphics.drawImage(coloredImage, 0, 0, null);

ImageIO.write(blackNWhite, "png", new File("/home/abc/newBlackNWhite.png"));

Answer 1

如果你想控制所谓的阈值处理过程,这里就是一个现成的代码片段.从128开始作为阈值,然后你得到其他方法的作用.

/**
 * Converts an image to a binary one based on given threshold
 * @param image the image to convert. Remains untouched.
 * @param threshold the threshold in [0,255]
 * @return a new BufferedImage instance of TYPE_BYTE_GRAY with only 0'S and 255's
 */
public static BufferedImage thresholdImage(BufferedImage image, int threshold) {
    BufferedImage result = new BufferedImage(image.getWidth(), image.getHeight(), BufferedImage.TYPE_BYTE_GRAY);
    result.getGraphics().drawImage(image, 0, 0, null);
    WritableRaster raster = result.getRaster();
    int[] pixels = new int[image.getWidth()];
    for (int y = 0; y < image.getHeight(); y++) {
        raster.getPixels(0, y, image.getWidth(), 1, pixels);
        for (int i = 0; i < pixels.length; i++) {
            if (pixels[i] < threshold) pixels[i] = 0;
            else pixels[i] = 255;
        }
        raster.setPixels(0, y, image.getWidth(), 1, pixels);
    }
    return result;
}