在 Android 中使用 colorMatrix 使黑色变暗

Question

我目前有以下代码来获取位图对象，去除颜色，然后将其变成红色，这可以工作，但我需要图像的较暗元素变得更暗，目前就像有人在图像上放了红色胶片一样，这几乎是我想要的，但需要黑色更暗：

Bitmap sourceBitmap = BitmapFactory.decodeFile(imgPath);
        float[] colorTransform = {
                0, 1f, 0, 0, 0, 
                0, 0, 0f, 0, 0,
                0, 0, 0, 0f, 0, 
                0, 0, 0, 1f, 0};
        ColorMatrix colorMatrix = new ColorMatrix();
        colorMatrix.setSaturation(0f); //Remove Colour 
        colorMatrix.set(colorTransform); //Apply the Red

        ColorMatrixColorFilter colorFilter = new ColorMatrixColorFilter(colorMatrix);
        Paint paint = new Paint();
        paint.setColorFilter(colorFilter);   

        Display display = getWindowManager().getDefaultDisplay(); 

        Bitmap resultBitmap = Bitmap.createBitmap(sourceBitmap, 0, (int)(display.getHeight() * 0.15), display.getWidth(), (int)(display.getHeight() * 0.75));            

        image.setImageBitmap(resultBitmap);

        Canvas canvas = new Canvas(resultBitmap);
        canvas.drawBitmap(resultBitmap, 0, 0, paint);

Answer 1

颜色矩阵中前三个原始数据的最后一列会改变图像的亮度。它在 [-255...255] 之间变化。 -255 会给你黑色图像，255 会给你白色图像。
此方法可以改变对比度。较亮的物体会变得更亮，较暗的物体会变得更暗。您可以将亮度设置为所需的位置。对比度在 [-1...1] 之间变化。

private static void setContrast(ColorMatrix cm, float contrast) {
                float scale = contrast + 1.f;
                   float translate = (-.5f * scale + .5f) * 255.f;
                cm.set(new float[] {
                       scale, 0, 0, 0, translate,
                       0, scale, 0, 0, translate,
                       0, 0, scale, 0, translate,
                       0, 0, 0, 1, 0 });
        }

Answer 2

c = 2;//this will boost your contrast by 2x thus deepening the black (and lightning the white). I'm not sure why at 0 you have anything but black... maybe I don't understand the matrix as well as I think I do... I thought 1 (in place of my c) gets you the original colors.

Anyway... give that a whirl. 


float[] colorTransform = {
                c, 1f, 0, 0, 0, 
                0, c, 0f, 0, 0,
                0, 0, c, 0f, 0, 
                0, 0, 0, 1f, 0};