Java 如何使位图变亮或变暗

例如，如何获取现有位图

Bitmap bm = BitmapFactory.decodeResource(getResources(), R.drawable.somebitmap);

并编写一个方法，返回位图的变暗版本

private Bitmap darkenBitMap(Bitmap bm) { }

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到目前为止，我一直在尝试使用Paint和Canvas，但没有结果。

下面是一个在每个像素上迭代的示例

/**
 * @param bitmap a mutable bitmap instance.
 */
private void darkenBitmap(Bitmap bitmap) {
    int height = bitmap.getHeight();
    int width = bitmap.getWidth();
    int pixel;

    // Iterate over each row (y-axis)
    for (int y = 0; y < height; y++) {
        // and each column (x-axis) on that row
        for (int x = 0; x < width; x++) {
            pixel = bitmap.getPixel(x, y);

            // TODO: Modify your pixel here. For samples, http://stackoverflow.com/questions/4928772/android-color-darker

            bitmap.setPixel(x, y, pixel);
        }
    }
}

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您还可以在该方法中创建一个新的可变位图，调用setPixel（…）并返回它。但是，如果可能的话，我强烈建议避免这种内存分配。

我终于明白了。希望它能帮助别人

private Bitmap darkenBitMap(Bitmap bm) {

    Canvas canvas = new Canvas(bm);
    Paint p = new Paint(Color.RED);
    //ColorFilter filter = new LightingColorFilter(0xFFFFFFFF , 0x00222222); // lighten
    ColorFilter filter = new LightingColorFilter(0xFF7F7F7F, 0x00000000);    // darken
    p.setColorFilter(filter);
    canvas.drawBitmap(bm, new Matrix(), p);

    return bm;
}

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使视野更暗。

canvas.drawARGB（200,0,0,0）

简而言之：）
根据序言的答案，这里有一个函数，可以将较暗的位图转换为较亮的位图。你所要做的就是传递一个介于0和100之间的数字（0表示较暗，100表示较亮）

如果您不想将其永久变暗并保存到磁盘、共享等，则可能需要使用过滤器。。。下面是一些参考资料，虽然这段代码可能会回答这个问题，但提供关于如何和/或为什么解决问题的额外上下文将提高答案的长期价值。请阅读原因
private Bitmap darkenBitMap(Bitmap bm) {

    Canvas canvas = new Canvas(bm);
    Paint p = new Paint(Color.RED);
    //ColorFilter filter = new LightingColorFilter(0xFFFFFFFF , 0x00222222); // lighten
    ColorFilter filter = new LightingColorFilter(0xFF7F7F7F, 0x00000000);    // darken
    p.setColorFilter(filter);
    canvas.drawBitmap(bm, new Matrix(), p);

    return bm;
}

private Bitmap darkenBitMap(Bitmap bm) {
    Canvas canvas = new Canvas(bm);
    canvas.drawARGB(1,0,0,0);
    canvas.drawBitmap(bm, new Matrix(), new Paint());
    return bm;
}

public void grayscaleImage(Bitmap bitmap, int lighten)
{
    Bitmap bmpGrayscale = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Bitmap.Config.ARGB_8888);
    Canvas c = new Canvas(bmpGrayscale);

    Paint grayscalePaint = new Paint();
    ColorMatrix cm = new ColorMatrix();
    cm.setSaturation(0);
    grayscalePaint.setColorFilter(new ColorMatrixColorFilter(cm));
    c.drawBitmap(bitmap, new Matrix(), grayscalePaint);

    ArgbEvaluator evaluator = new ArgbEvaluator();

    float fraction = lighten / 100.0F;

    int mul = (int) evaluator.evaluate(fraction, 0xFF7F7F7F, 0xFFFFFFFF);
    int add = (int) evaluator.evaluate(fraction, 0x00000000, 0x00222222);

    Paint lighteningPaint = new Paint();
    lighteningPaint.setColorFilter(new LightingColorFilter(mul, add));
    c.drawBitmap(bmpGrayscale, new Matrix(), lighteningPaint);

    setImageBitmap(bmpGrayscale);
}