android - 同时设置 Saturation 和 ColorFilter 图像

Question

下面的函数成功改变了图片的对比度和亮度。

Bitmap bmp;
ImageView alteredImageView;
...
public void drawAlteredImage(float contr,float bright) {
    Bitmap alteredBitmap = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());
    Canvas canvas = new Canvas(alteredBitmap);
    Paint paint = new Paint();
    ColorMatrix cm = new ColorMatrix();

    cm.set(new float[] { 
            contr, 0, 0, 0, bright, 
            0, contr, 0, 0, bright, 
            0, 0, contr, 0, bright, 
            0, 0, 0, 1, 0 });

    paint.setColorFilter(new ColorMatrixColorFilter(cm));
    Matrix matrix = new Matrix();
    canvas.drawBitmap(bmp, matrix, paint);
    alteredImageView.setImageBitmap(alteredBitmap);
}

但是当我将 setSaturation 方法添加到 ColorMatrix 时，对比度和亮度更改停止工作。代码:

public void drawAlteredImage(float contr,float bright,float satur) {
    Bitmap alteredBitmap = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());
    Canvas canvas = new Canvas(alteredBitmap);
    Paint paint = new Paint();
    ColorMatrix cm = new ColorMatrix();

    cm.set(new float[] { 
            contr, 0, 0, 0, bright, 
            0, contr, 0, 0, bright, 
            0, 0, contr, 0, bright, 
            0, 0, 0, 1, 0 });
    cm.setSaturation(satur);
    paint.setColorFilter(new ColorMatrixColorFilter(cm));
    Matrix matrix = new Matrix();
    canvas.drawBitmap(bmp, matrix, paint);
    alteredImageView.setImageBitmap(alteredBitmap);
}

在这种情况下仅应用饱和效果。为什么会出现这个问题？我该如何解决？

Answer 1

setSaturation(...) 方法替换矩阵中的所有值。您可以创建一个结合了这两种操作的矩阵，或者使用两个单独的 drawBitmap(...) 调用来执行这些操作。

尝试:

cm.setSaturation(satur);
final float m[] = cm.getArray();
final float c = contr;
cm.set(new float[] { 
        m[ 0] * c, m[ 1] * c, m[ 2] * c, m[ 3] * c, m[ 4] * c + bright, 
        m[ 5] * c, m[ 6] * c, m[ 7] * c, m[ 8] * c, m[ 9] * c + bright, 
        m[10] * c, m[11] * c, m[12] * c, m[13] * c, m[14] * c + bright, 
        m[15]    , m[16]    , m[17]    , m[18]    , m[19] });