如何优化此图像处理用最接近的可用RGB替换图像上的所有像素？ [英] how to optimized this image processing replace all pixels on image with closest available RGB?

问题描述

我试图用最接近的可用RGB替换输入图像的所有像素。我有一个包含颜色和输入图像的数组。这是我的代码，它给我一个预期的输出图像，但是处理一个图像需要很长的时间（大约一分钟）。任何人都可以帮我改进代码吗？或者，如果您有任何其他建议，请帮助。

Im' trying to replace all pixels of input image with closest available RGB. I have a array contain color and input image. Here is my code, it give me an output image as expected, BUT it take very LONG time( about a min) to process one image. Can anybody help me improve the code? Or if you have any other suggestions, please help.

 UIGraphicsBeginImageContextWithOptions(CGSizeMake(CGImageGetWidth(sourceImage),CGImageGetHeight(sourceImage)), NO, 0.0f);
 //Context size I keep as same as original input image size

 //Otherwise, the output will be only a partial image
 CGContextRef context; 
 context = UIGraphicsGetCurrentContext();

 //This is for flipping up sidedown
 CGContextTranslateCTM(context, 0, self.imageViewArea.image.size.height);
 CGContextScaleCTM(context, 1.0, -1.0);



        // init vars
        float d   = 0;                           // squared error
        int idx = 0;                             // index of palette color
        int min = 1000000;                       // min difference
        UIColor *oneRGB;                         // color at a pixel
        UIColor *paletteRGB;                     // palette color



        // visit each output color and determine closest color from palette
        for(int y=0; y<sizeY; y++) {
            for(int x=0; x<sizeX; x++) {
                // desired (avg) color is one pixel of scaled image
                oneRGB = [inputImgAvg colorAtPixel:CGPointMake(x,y)];


                // find closest color match in palette: init idx with index
                // of closest match; keep track of min to find idx
                min = 1000000;
                idx = 0;

                CGContextDrawImage(context,CGRectMake(xx, yy, 1, 1),img);
            }
        }

        UIImage *output = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        self.imageViewArea.image = output;

推荐答案

通常的答案是使用 kd tree 或其他一些八叉树结构，以减少每个像素必须完成的计算和比较次数。

The usual answer is to use a k-d tree or some other Octree structure to reduce the number of computations and comparisons that have to be done at each pixel.

我是也成功地将色彩空间划分为规则网格，并为网格的每个部分保留可能最接近的匹配列表。例如，您可以将R，G，B的（0-255）值除以16，最后得到一个（16,16,16）或4096个元素的网格。最好的情况是，特定网格元素的列表中只有一个成员，根本不需要遍历列表。

I've also had success with partitioning the color space into a regular grid and keeping a list of possible closest matches for each part of the grid. For example you can divide the (0-255) values of R,G,B by 16 and end up with a grid of (16,16,16) or 4096 elements altogether. Best case is that there's only one member of the list for a particular grid element and no need to traverse the list at all.

这篇关于如何优化此图像处理用最接近的可用RGB替换图像上的所有像素？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！