How To Use The Renderscript Blurring Effect Without Artifacts?

Background There are plenty of places (including here) to show how to use Renderscript to blur images, as such: @TargetApi(VERSION_CODES.JELLY_BEAN_MR1) public static Bitmap render

Solution 1:

The problem was with the algorithm I used. Thanks to this github project, I've found the issue (which is probably not using the correct type fot the allocation) and used a nicer approach:

private static final AtomicReference<RenderScript> sRenderscript = new AtomicReference<>();


public static Bitmap blur(Context context, Bitmap bitmap) {
    return blur(context, bitmap, 4, false, false);
}

public static Bitmap blur(Context context, Bitmap bitmap, float radius) {
    return blur(context, bitmap, radius, false, false);
}

public static Bitmap blur(Context context, Bitmap bitmapOriginal, @FloatRange(from = 0.0f, to = 25.0f) float radius, boolean overrideOriginal, boolean recycleOriginal) {
    if (bitmapOriginal == null || bitmapOriginal.isRecycled())
        return null;
    RenderScript rs = sRenderscript.get();
    if (rs == null)
        if (!sRenderscript.compareAndSet(null, rs = RenderScript.create(context)) && rs != null)
            rs.destroy();
        else
            rs = sRenderscript.get();
    final Bitmap inputBitmap = bitmapOriginal.getConfig() == Config.ARGB_8888 ? bitmapOriginal : bitmapOriginal.copy(Config.ARGB_8888, true);
    final Bitmap outputBitmap = overrideOriginal ? bitmapOriginal : Bitmap.createBitmap(bitmapOriginal.getWidth(), bitmapOriginal.getHeight(), Config.ARGB_8888);
    final Allocation input = Allocation.createFromBitmap(rs, inputBitmap);
    final Allocation output = Allocation.createTyped(rs, input.getType());
    final ScriptIntrinsicBlur script = ScriptIntrinsicBlur.create(rs, Element.U8_4(rs));
    script.setRadius(radius);
    script.setInput(input);
    script.forEach(output);
    if (recycleOriginal && !overrideOriginal)
        bitmapOriginal.recycle();
    output.copyTo(outputBitmap);
    return outputBitmap;
}

Now it all works nicely.

Solution 2:

The artifact in the original version is because the same input Allocation was used as the output Allocation for IntrinsicBlur:

    blur.setInput(overlayAlloc);
    blur.setRadius(radius);
    blur.forEach(overlayAlloc);

forEach(aOut) computes the Gaussian blur and saves the result to the output Allocation. Since the algorithm requires information about the neighbors, doing blur in place may corrupt the input data for sub-sequent calculations.

Solution 3:

I use code below. It worked!

public static Bitmap blurRenderScript(Context context, Bitmap inputBitmap, int radius) {
    Bitmap outputBitmap = inputBitmap.copy(inputBitmap.getConfig(), true);
    RenderScript renderScript = RenderScript.create(context);
    Allocation blurInput = Allocation.createFromBitmap(renderScript, inputBitmap, Allocation.MipmapControl.MIPMAP_NONE, Allocation.USAGE_SCRIPT);
    Allocation blurOutput = Allocation.createFromBitmap(renderScript, outputBitmap);
    ScriptIntrinsicBlur blur = ScriptIntrinsicBlur.create(renderScript,
            Element.U8_4(renderScript));
    blur.setInput(blurInput);
    blur.setRadius(radius); // radius must be 0 < r <= 25
    blur.forEach(blurOutput);
    blurOutput.copyTo(outputBitmap);
    renderScript.destroy();

    return outputBitmap;
}

in build.Gradle

defaultConfig {
    applicationId "hello.test.app"
    minSdkVersion 16
    targetSdkVersion 22
    versionCode 1
    versionName "1.0"
    renderscriptTargetApi 18
    renderscriptSupportModeEnabled true
}