Question

如何使用现有的位图，比如说

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

并编写一个返回位图的黑暗版本的方法？

private Bitmap darkenBitMap(Bitmap bm) { }

到目前为止，我一直在尝试使用Paint和Canvas，没有任何结果。

Answer 1

我终于明白了。希望它可以帮助别人。

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;
}

Answer 2

这是一个迭代每个像素的示例。

/**
 * @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);
        }
    }
}

该方法需要可变位图，因此您可能需要使用BitmapFactory选项加载位图。如，

BitmapFactory.Options options = new BitmapFactory.Options();
options.inMutable = true;
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.somebitmap, options);

你也可以在该方法中创建一个新的可变位图，在其上调用setPixel（...）并返回它。但是，如果可能的话，我强烈建议避免使用这种内存分配。

Answer 3

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;
}

Answer 4

以the_prole的答案为基础，此功能可以将较暗的位图转换为较亮的位图。您所要做的就是传递0到100之间的数字（0较暗，100较亮）。

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);
}

Answer 5

让视图变暗。

canvas.drawARGB(200, 0, 0, 0);

简短而简单：）

如何使位图变亮或变暗

5 个答案: