A method that uses RenderScript to downscale an image without aliasing.

renderscriptresize.java

public static Bitmap resizeBitmap2(RenderScript rs, Bitmap src, int dstWidth) {
        Bitmap.Config  bitmapConfig = src.getConfig();
        int srcWidth = src.getWidth();
        int srcHeight = src.getHeight();
        float srcAspectRatio = (float) srcWidth / srcHeight;
        int dstHeight = (int) (dstWidth / srcAspectRatio);

        float resizeRatio = (float) srcWidth / dstWidth;

        /* Calculate gaussian's radius */
        float sigma = resizeRatio / (float) Math.PI;
        // https://android.googlesource.com/platform/frameworks/rs/+/master/cpu_ref/rsCpuIntrinsicBlur.cpp
        float radius = 2.5f * sigma - 1.5f;
        radius = Math.min(25, Math.max(0.0001f, radius));

        /* Gaussian filter */
        Allocation tmpIn = Allocation.createFromBitmap(rs, src);
        Allocation tmpFiltered = Allocation.createTyped(rs, tmpIn.getType());
        ScriptIntrinsicBlur blurInstrinsic = ScriptIntrinsicBlur.create(rs, tmpIn.getElement());

        blurInstrinsic.setRadius(radius);
        blurInstrinsic.setInput(tmpIn);
        blurInstrinsic.forEach(tmpFiltered);

        tmpIn.destroy();
        blurInstrinsic.destroy();

        /* Resize */
        Bitmap dst = Bitmap.createBitmap(dstWidth, dstHeight, bitmapConfig);
        Type t = Type.createXY(rs, tmpFiltered.getElement(), dstWidth, dstHeight);
        Allocation tmpOut = Allocation.createTyped(rs, t);
        ScriptIntrinsicResize resizeIntrinsic = ScriptIntrinsicResize.create(rs);

        resizeIntrinsic.setInput(tmpFiltered);
        resizeIntrinsic.forEach_bicubic(tmpOut);
        tmpOut.copyTo(dst);

        tmpFiltered.destroy();
        tmpOut.destroy();
        resizeIntrinsic.destroy();

        return dst;
    }

The method is mentioned in this article.

I have problem with this resize metod. One user reported that graphics are not fully loaded (screen: https://kenumir.pl/tests/resize-problem.png) - anyone have same issue?