如何以编程方式更改android中位图的对比度? [英] How to programmatically change contrast of a bitmap in android?

问题描述

我想以编程方式更改位图的对比度.到目前为止，我已经尝试过了.

I want to programmatically change the contrast of bitmap. Till now I have tried this.

private Bitmap adjustedContrast(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.green(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.blue(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;
    }

但这并没有按预期工作.请在这方面帮助我或提供任何其他解决方案来实现这一目标.提前致谢.

But this does not work as expected. Please help me in this or provide any other solution to achieve this. Thanks in advance.

推荐答案

试试这个.您的代码不起作用，因为您只创建了一个可变位图，并且如果我没记错的话，并没有将源位图的图像复制到可变位图.

Try this. Your code didn't work because you create only a mutable bitmap and didn't copy the image of source bitmap to the mutable one if i'm not mistaken.

希望有帮助:)

private Bitmap adjustedContrast(Bitmap src, double value)
{
    // image size
    int width = src.getWidth();
    int height = src.getHeight();
    // create output bitmap

    // create a mutable empty bitmap
    Bitmap bmOut = Bitmap.createBitmap(width, height, src.getConfig());

    // create a canvas so that we can draw the bmOut Bitmap from source bitmap
    Canvas c = new Canvas();
    c.setBitmap(bmOut);

    // draw bitmap to bmOut from src bitmap so we can modify it
    c.drawBitmap(src, 0, 0, new Paint(Color.BLACK));


    // 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.green(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.blue(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;
}

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