Jagged edges on images rendered in Android

Question

I'm currently developing my first Android app and am having some issues rendering images. The image itself is great quality to begin with, but upon rendering it the quality drastically lowers. Edges become jagged and it just looks poorly done. Everyone I've showed it to thus far has almost immediately noticed it, without any prompting about it. [start on left, end on right:]

I'm trying everything I am aware of and every tip I've been able to find by looking around online, but nothing seems to fix it.

Currently, I get the image as a Bitmap and scale it:

Bitmap holeImage = BitmapFactory.decodeResource(res, R.drawable.hole_image);
Bitmap holeImageBMP = Bitmap.createScaledBitmap(holeImage, width, height, true);

Once I have the image, I create a Paint, set a few smoothing attributes to true, and then draw it on the canvas:

Paint smoothingPaint = new Paint();
smoothingPaint.setAntiAlias(true);
smoothingPaint.setFilterBitmap(true);
smoothingPaint.setDither(true);
canvas.drawBitmap(holeImageBMP, 0, 0, smoothingPaint);

Yet, as you can obviously see above, the image quality drastically decreases. I've seen plenty of images being rendered beautifully and I'm honestly just not sure what's going on so any advice would be great!

Other notes: I'm using a SurfaceView method to handle the drawing, similar in nature to the LunarLander example given in the SDK.

Thanks again!

Answer 1

If you aren't restricted to much less colors than the original picture has (Does Android have 256 color modes?), I'd suggest to disable dithering , if you zoom into your picture, it does have a visible effect that perhaps destroys a smooth look.

I think in your case, dithering infers with anti-aliasing by destroying the additional colors that anti-aliasing needs for a smooth look. A quick color count on your pictures (left one about 850, right one about 140) confirms this.

Answer 2

That is probably related to converting images from one format to another. Also, android screens vary from device to device. Try to use another device and it might look better... Almost for sure it will have a different tone.

Try to read this great article on this problem (and banding and dithering) and consider adapting the image you created for it to work better in android devices: http://www.curious-creature.org/2010/12/08/bitmap-quality-banding-and-dithering/