opencv - IplImage 像素访问 JavaCV

Question

我正在尝试逐个访问 IplImage 的像素。我正在使用 Java 和 Processing，有时我需要逐个像素地访问。到目前为止我已经这样做了，但我不知道出了什么问题:

public IplImage PImageToIplImage(PImage imageSrc)
    {
        IplImage imageDst;
        if(imageSrc.format==RGB)
        {
            imageDst = IplImage.create(imageSrc.width, imageSrc.height, IPL_DEPTH_8U, 3);
            ByteBuffer imagePixels=imageDst.getByteBuffer();
            int locPImage, locIplImage, x, y;
            for(y=0; y<imageSrc.height; y++)
                for(x=0; x<imageSrc.width; x++)
                {
                    locPImage = x + y * width;
                    locIplImage=y*imageDst.widthStep()+3*x;
                    imagePixels.put(locIplImage+2, (byte)(red(imageSrc.pixels[locPImage])));
                    imagePixels.put(locIplImage+1, (byte)(green(imageSrc.pixels[locPImage])));
                    imagePixels.put(locIplImage, (byte)(blue(imageSrc.pixels[locPImage])));
                }
        }
}

经过Karlphilip sugestion，我来到这里，还是不行。当我尝试显示时，它给了我一个 nullPointer 异常:

imageDst = IplImage.create(imageSrc.width, imageSrc.height, IPL_DEPTH_8U, 3);
CvMat imagePixels = CvMat.createHeader(imageDst.height(), imageDst.width(), CV_32FC1);  
cvGetMat(imageDst, imagePixels, null, 0); 
int locPImage, x, y;
for(y=0; y<imageSrc.height; y++)
   for(x=0; x<imageSrc.width; x++)
   {
       locPImage = x + y * width;
       CvScalar scalar = new CvScalar();
       scalar.setVal(0, red(imageSrc.pixels[locPImage]));
       scalar.setVal(1, green(imageSrc.pixels[locPImage]));
       scalar.setVal(2, blue(imageSrc.pixels[locPImage]));
       cvSet2D(imagePixels, y, x, scalar);
   }
   imageDst = new IplImage(imagePixels); 

Answer 1

在 JavaCV 中迭代每个像素的最快方法是:

ByteBuffer buffer = image.getByteBuffer();

for(int y = 0; y < image.height(); y++) {
    for(int x = 0; x < image.width(); x++) {
        int index = y * image.widthStep() + x * image.nChannels();

        // Used to read the pixel value - the 0xFF is needed to cast from
        // an unsigned byte to an int.
        int value = buffer.get(index) & 0xFF;

        // Sets the pixel to a value (greyscale).
        buffer.put(index, value);

        // Sets the pixel to a value (RGB, stored in BGR order).
        buffer.put(index, blue);
        buffer.put(index + 1, green);
        buffer.put(index + 2, red);
    }
}