从 java 中的 [0,255] 个灰度值数组创建灰度位图

Question

我有一个数组 int[] shadesOfGray 大小 n*n 包含来自 [0,255] 的值。是否可以从该数组创建 8 位灰度位图？

例如，如果 int[] shadesOfGray = {255, 255, 255, 128, 128, 128, 0, 0, 0}

则位图中对应像素的强度为：

255 255 255
128 128 128
0    0   0

我试过这样的事情：

   private static void generateBMPwithDistribution(int[] shadesOfGray, int sum, String path) throws IOException {

        int dim = 100;  
        byte[] buffer = new byte[dim * dim];    

        for (int x = 0, i = 0; x < dim; x++)        
            for (int y = 0; y < dim; y++)                                              
                buffer[(x * dim) + y] = (byte) (shadesOfGray[i]); // problem  

        try {
            ImageIO.write(getGrayscale(dim, buffer), "bmp", new File(path));
        } catch (IOException e) {
            ...
        }

    }

    public static BufferedImage getGrayscale(int width, byte[] buffer) {
        int height = buffer.length / width;
        ColorSpace cs = ColorSpace.getInstance(ColorSpace.CS_GRAY);
        int[] nBits = { 8 };
        ColorModel cm = new ComponentColorModel(cs, nBits, false, true,
                Transparency.OPAQUE, DataBuffer.TYPE_BYTE);
        SampleModel sm = cm.createCompatibleSampleModel(width, height);
        DataBufferByte db = new DataBufferByte(buffer, buffer.length);
        WritableRaster raster = Raster.createWritableRaster(sm, db, null);
        BufferedImage result = new BufferedImage(cm, raster, false, null);

        return result;
    }

因为我想要 8 位 .bmp，所以我正在复制缓冲区中的值，然后将缓冲区写入文件。问题是值 >= 128；字节被认为具有负值。 Java 有办法克服这个问题吗？

Answer 1

您的程序可能如下所示：

private static void generateBMPwithDistribution(int[] shadesOfGray, int sum, String path) throws IOException {

    int dim1 = (int)Math.sqrt(shadesOfGray.length), dim=100*dim1;
    int[] buffer = new int[dim * dim];    

    int howManyTimes=dim/dim1;
    for (int x = 0; x < dim; x++)        
        for (int y = 0; y < dim; y++) {                                             
            int valueToReplicate=shadesOfGray[(x + y*dim)/howManyTimes];
            buffer[x + y*dim] = 0xff000000|(valueToReplicate<<16)|(valueToReplicate<<8)|valueToReplicate;
        }

    BufferedImage result=new BufferedImage(dim, dim, BufferedImage.TYPE_INT_RGB);

    try {
        ImageIO.write(result, "bmp", new File(path));
    } catch (IOException e) {
        ...
    }

}

从 java 中的 [0,255] 个灰度值数组创建灰度位图

Creating grayscale bitmap from array of [0,255] gray values in java

java

bitmap

image-processing

bmp