24 bpp的转换位图1bpp [英] Convert 24bpp Bitmap to 1bpp

问题描述

我想转换一个小的位图图像。我想因为这是不是白100％转换为黑色的任何像素。我曾尝试

I am trying to convert a small bitmap image. I would like for any pixel that is not 100% white to be converted to black. I have tried

Bitmap output = sourceImage.Clone(new Rectangle(0, 0, sourceImage.Width, sourceImage.Height), PixelFormat.Format1bppIndexed);

还有，在1bpp输出白呆了几个打火机像素。什么是实现这种转换的最快方法？我可以修改呼叫的强度阈值克隆（）？

There are still a few lighter pixels that stay white in the 1bpp output. What is the fastest way to achieve this conversion? Can I modify the intensity threshold of the call to Clone()?

推荐答案

试试这个，从非常快速1bpp转换

从这里<重复href=\"http://stackoverflow.com/questions/17192800/threshold-value-when-converting-image-to-1bpp\">Threshold图像转换值时，1bpp？。

        private static unsafe void Convert(Bitmap src, Bitmap conv)
        {
            // Lock source and destination in memory for unsafe access
            var bmbo = src.LockBits(new Rectangle(0, 0, src.Width, src.Height), ImageLockMode.ReadOnly,
                                     src.PixelFormat);
            var bmdn = conv.LockBits(new Rectangle(0, 0, conv.Width, conv.Height), ImageLockMode.ReadWrite,
                                     conv.PixelFormat);

            var srcScan0 = bmbo.Scan0;
            var convScan0 = bmdn.Scan0;

            var srcStride = bmbo.Stride;
            var convStride = bmdn.Stride;

            byte* sourcePixels = (byte*)(void*)srcScan0;
            byte* destPixels = (byte*)(void*)convScan0;

            var srcLineIdx = 0;
            var convLineIdx = 0;
            var hmax = src.Height-1;
            var wmax = src.Width-1;
            for (int y = 0; y < hmax; y++)
            {
                // find indexes for source/destination lines

                // use addition, not multiplication?
                srcLineIdx += srcStride;
                convLineIdx += convStride;

                var srcIdx = srcLineIdx;
                for (int x = 0; x < wmax; x++)
                {
                    // index for source pixel (32bbp, rgba format)
                    srcIdx += 4;
                    //var r = pixel[2];
                    //var g = pixel[1];
                    //var b = pixel[0];

                    // could just check directly?
                    //if (Color.FromArgb(r,g,b).GetBrightness() > 0.01f)
                    if (!(sourcePixels[srcIdx] == 0 && sourcePixels[srcIdx + 1] == 0 && sourcePixels[srcIdx + 2] == 0))
                    {
                        // destination byte for pixel (1bpp, ie 8pixels per byte)
                        var idx = convLineIdx + (x >> 3);
                        // mask out pixel bit in destination byte
                        destPixels[idx] |= (byte)(0x80 >> (x & 0x7));
                    }
                }
            }
            src.UnlockBits(bmbo);
            conv.UnlockBits(bmdn);
        }

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