如何在BufferedImage中设置RGB像素以显示16位深度的PNG？ [英] How to set RGB pixel in a BufferedImage to display a 16-bit-depth PNG?

问题描述

我正在尝试读取并显示PNG文件。 我可以轻松处理8位深度的图像。 我按如下方式进行：

BufferedImage result = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

然后我读取每个像素的3*8=24位，将它们保存在一个字节数组data中，并使用：

将它们放入图像中

for (int y = 0; y < height; y++)
   for (int x = 0; x < width; x++)
     result.setRGB(x, y, ((data[x * 3 + 0] & 0xff) << 16)
                       + ((data[x * 3 + 1] & 0xff) << 8)
                       + ((data[x * 3 + 2] & 0xff)));

现在问题出在16位深度图像上。当然，data现在更大了，它包含48位，分为6个字节，每个RGB三元组：来自调试器的data具有我期望的值。 如何设置RGB像素？我必须更改BufferedImage声明吗？可以使用：

BufferedImage result = new BufferedImage(width, height, BufferedImage.TYPE_USHORT_565_RGB);

提前表示感谢！

附注：按照PNG标准，图像的颜色类型为2(不含Alpha的RGB)。

---

也许我将不得不使用http://docs.oracle.com/javase/7/docs/api/java/awt/image/ColorModel.html

推荐答案

@haraldK指向了正确的方向。我提供了一些来自"icafe"Java图像库的PNGReader的工作代码。

if(bitsPerPixel == 16) {
    if(interlace_method==NON_INTERLACED)
       spixels = generate16BitRGBPixels(compr_data, false);
    else {
       spixels = generate16BitRGBInterlacedPixels(compr_data, false);
               }
    int[] off = {0, 1, 2}; //band offset, we have 3 bands
    int numOfBands = 3;
    boolean hasAlpha = false;
    int trans = Transparency.OPAQUE;
    int[] nBits = {16, 16, 16}; 
    if(alpha != null) { // Deal with single color transparency
       off = new int[] {0, 1, 2, 3}; //band offset, we have 4 bands
       numOfBands = 4;
       hasAlpha = true;
       trans = Transparency.TRANSLUCENT;
       nBits = new int[] {16, 16, 16, 16};                      
    }
    db = new DataBufferUShort(spixels, spixels.length);
    raster = Raster.createInterleavedRaster(db, width, height, width*numOfBands, numOfBands, off, null);
    cm = new ComponentColorModel(colorSpace, nBits, hasAlpha, false, trans, DataBuffer.TYPE_USHORT);
}
return new BufferedImage(cm, raster, false, null);

以下是Generate16BitRGBPixels()方法：

private short[] generate16BitRGBPixels(byte[] compr_data, boolean fullAlpha) throws Exception {
     //
     int bytesPerPixel = 0;
     byte[] pixBytes;

     if (fullAlpha)
         bytesPerPixel = 8;
     else 
         bytesPerPixel = 6;

     bytesPerScanLine = width*bytesPerPixel;         

     // Now inflate the data.
     pixBytes = new byte[height * bytesPerScanLine];

     // Wrap an InflaterInputStream with a bufferedInputStream to speed up reading
     BufferedInputStream bis = new BufferedInputStream(new InflaterInputStream(new ByteArrayInputStream(compr_data)));

     apply_defilter(bis, pixBytes, height, bytesPerPixel, bytesPerScanLine);

     short[] spixels = null;

     if(alpha != null) { // Deal with single color transparency
         spixels = new short[width*height*4];
         short redMask = (short)((alpha[1]&0xff)|(alpha[0]&0xff)<<8);
         short greenMask = (short)((alpha[3]&0xff)|(alpha[2]&0xff)<<8);;
         short blueMask = (short)((alpha[5]&0xff)|(alpha[4]&0xff)<<8);

         for(int i = 0, index = 0; i < pixBytes.length; index += 4) {
             short red = (short)((pixBytes[i++]&0xff)<<8|(pixBytes[i++]&0xff));
             short green = (short)((pixBytes[i++]&0xff)<<8|(pixBytes[i++]&0xff));
             short blue = (short)((pixBytes[i++]&0xff)<<8|(pixBytes[i++]&0xff));
             spixels[index] = red;
             spixels[index + 1] = green;
             spixels[index + 2] = blue;
             if(spixels[index] == redMask && spixels[index + 1] == greenMask && spixels[index + 2] == blueMask) {
                 spixels[index + 3] = (short)0x0000;                               
             } else {
                 spixels[index + 3] = (short)0xffff;
             }
         }
     } else
         spixels = ArrayUtils.toShortArray(pixBytes, true);

     return spixels;         
 }

和ArrayUtils.toShortArray()方法：

public static short[] toShortArray(byte[] data, int offset, int len, boolean bigEndian) {

    ByteBuffer byteBuffer = ByteBuffer.wrap(data, offset, len);

    if (bigEndian) {
        byteBuffer.order(ByteOrder.BIG_ENDIAN);
    } else {
        byteBuffer.order(ByteOrder.LITTLE_ENDIAN);
    }

    ShortBuffer shortBuf = byteBuffer.asShortBuffer();
    short[] array = new short[shortBuf.remaining()];
    shortBuf.get(array);

    return array;
}

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