Transparency utils

gistfile1.java

/**
* Adds a transparent gradient to the right edge of a bitmap
*
* Released into the public domain
*
* Created by chedabob on 05/04/2014.
* https://gist.github.com/chedabob/9994080
*
*/

 /**
* Adds a transparent gradient to the right edge of the image
* @param input The input bitmap
* @param fadeStartPercentage The percentage of the image to start the fade at (expressed as 0.0f >= x <= 1.0f)
* @return Bitmap with gradient applied
*/
private static Bitmap transFadeRightEdge(Bitmap input, float fadeStartPercentage) {

        int width = input.getWidth();
        int height = input.getHeight();

        int[] outPixels = new int[width * height];
        input.getPixels(outPixels, 0, width, 0, 0, width, height);

        int widthFadePixel = (int) (width * fadeStartPercentage);
        float fadeWidth = (float) (width - widthFadePixel);

        int xAlpha = 0;
        int index = 0;
        int indexStart = (height - 1) * width;

        for (int x = widthFadePixel; x < width; ++x) {
            xAlpha = ((int) ((1.0f - ((float) (x - widthFadePixel) / fadeWidth)) * 255)) << 24;

            index = indexStart + x;
            // Internal loop runs faster when run in reverse
            for (; index >= 0; index -= width) {
                outPixels[index] = (outPixels[index] & 0x00ffffff) | xAlpha;
            }
        }

        return Bitmap.createBitmap(outPixels, width, height, Bitmap.Config.ARGB_8888);
    }