拍摄单色照片（黑白）与Android [英] Take monochrome picture (black and white) with Android

问题描述

我想借此真正的黑色和白色的照片在我的应用程序。我搜索的解决方案（在这个网站太），但我总能找到解决方案，把灰度照片（例如，在<一个href="http://stackoverflow.com/questions/9377786/android-converting-a-bitmap-to-a-monochrome-bitmap-1-bit-per-pixel">this话题），但它不是我所期待的......

I would like to take a picture in true black and white in my app. I searched for solutions (in this site too), but I always found solution to put a photo in gray scale (for example in this topic), but it's not what I am looking for ...

我还发现了一个话题提出这样的：

I also found a topic proposing this :

public static Bitmap createContrast(Bitmap src, double value) {
// image size

                int width = src.getWidth();
                int height = src.getHeight();
                // create output bitmap
                Bitmap bmOut = Bitmap.createBitmap(width, height, src.getConfig());
                // color information
                int A, R, G, B;
                int pixel;
                // get contrast value
                double contrast = Math.pow((100 + value) / 100, 2);

        // scan through all pixels
        for (int x = 0; x < width; ++x) {
            for (int y = 0; y < height; ++y) {
                // get pixel color
                pixel = src.getPixel(x, y);
                A = Color.alpha(pixel);
                // apply filter contrast for every channel R, G, B
                R = Color.red(pixel);
                R = (int) (((((R / 255.0) - 0.5) * contrast) + 0.5) * 255.0);
                if (R < 0) {
                    R = 0;
                } else if (R > 255) {
                    R = 255;
                }

                G = Color.red(pixel);
                G = (int) (((((G / 255.0) - 0.5) * contrast) + 0.5) * 255.0);
                if (G < 0) {
                    G = 0;
                } else if (G > 255) {
                    G = 255;
                }

                B = Color.red(pixel);
                B = (int) (((((B / 255.0) - 0.5) * contrast) + 0.5) * 255.0);
                if (B < 0) {
                    B = 0;
                } else if (B > 255) {
                    B = 255;
                }

                // set new pixel color to output bitmap
                bmOut.setPixel(x, y, Color.argb(A, R, G, B));
            }
        }

        return bmOut;

    }

但图像质量是可怕的......

But the image quality is horrible ...

有没有人有一个想法吗？

Is anyone having an idea please?

感谢您

推荐答案

如果你喜欢的图像以1位黑/白，你可以用一个简单的（安培;慢）阈值算法

If you like the image to be 1bit black/white you can use a simple (& slow) threshold algorithm

public static Bitmap createBlackAndWhite(Bitmap src) {
    int width = src.getWidth();
    int height = src.getHeight();
    // create output bitmap
    Bitmap bmOut = Bitmap.createBitmap(width, height, src.getConfig());
    // color information
    int A, R, G, B;
    int pixel;

    // scan through all pixels
    for (int x = 0; x < width; ++x) {
        for (int y = 0; y < height; ++y) {
            // get pixel color
            pixel = src.getPixel(x, y);
            A = Color.alpha(pixel);
            R = Color.red(pixel);
            G = Color.green(pixel);
            B = Color.blue(pixel);
            int gray = (int) (0.2989 * R + 0.5870 * G + 0.1140 * B);

            // use 128 as threshold, above -> white, below -> black
            if (gray > 128) 
                gray = 255;
            else
                gray = 0;
            // set new pixel color to output bitmap
            bmOut.setPixel(x, y, Color.argb(A, gray, gray, gray));
        }
    }
    return bmOut;
}

不过，这取决于什么都不会好看，你需要一个抖动算法更好的效果，请参阅算法概述 - 这个人是阈值法

But depending on what that will not look good, for better results you need a dithering algorithm, see Algorithm overview - this one is the threshold method.

有关256级灰度转换：

For 256 levels of gray conversion:

根据<一href="http://www.mathworks.de/help/toolbox/images/ref/rgb2gray.html">http://www.mathworks.de/help/toolbox/images/ref/rgb2gray.html你计算每个像素的灰度值灰色= 0.2989 * R + 0.5870 * G + 0.1140 * B 这将转化为

according to http://www.mathworks.de/help/toolbox/images/ref/rgb2gray.html you calculate the gray value of each pixel as gray = 0.2989 * R + 0.5870 * G + 0.1140 * B which would translate to

public static Bitmap createGrayscale(Bitmap src) {
    int width = src.getWidth();
    int height = src.getHeight();
    // create output bitmap
    Bitmap bmOut = Bitmap.createBitmap(width, height, src.getConfig());
    // color information
    int A, R, G, B;
    int pixel;

    // scan through all pixels
    for (int x = 0; x < width; ++x) {
        for (int y = 0; y < height; ++y) {
            // get pixel color
            pixel = src.getPixel(x, y);
            A = Color.alpha(pixel);
            R = Color.red(pixel);
            G = Color.green(pixel);
            B = Color.blue(pixel);
            int gray = (int) (0.2989 * R + 0.5870 * G + 0.1140 * B);
            // set new pixel color to output bitmap
            bmOut.setPixel(x, y, Color.argb(A, gray, gray, gray));
        }
    }
    return bmOut;
}

但是，这是pretty的慢，因为你必须做的，对于千万像素的分别。

But that is pretty slow since you have to do that for millions of pixels separately.

http://stackoverflow.com/a/9377943/995891 的具有达到相同的好得多的方式。

http://stackoverflow.com/a/9377943/995891 has a much nicer way of achieving the same.

// code from that answer put into method from above
public static Bitmap createGrayscale(Bitmap src) {
    int width = src.getWidth();
    int height = src.getHeight();
    Bitmap bmOut = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(bmOut);
    ColorMatrix ma = new ColorMatrix();
    ma.setSaturation(0);
    Paint paint = new Paint();
    paint.setColorFilter(new ColorMatrixColorFilter(ma));
    canvas.drawBitmap(src, 0, 0, paint);
    return bmOut;
}

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