Question

I have a piece of code which draws an image to the background of the screen. The problem I am having is that the image looks poor, unless I use a Paint object with dithering set to true

Without a paint object, the canvas.drawBitmap() method takes roughly 15ms, with dithering, it can be up to more than three times that. As the application is intended to be a livewallpaper, this is of concern.

I have checked that the image is in ARGB_8888 format, but when drawn without the paint object, it looks closer to having 256 colors. I have tried using different image formats & bit-depths(32,24,16) but I still have this problem.

How come it is not possible to perform the dither on the image once, and use this version. Or why is my image being downsampled?

Answer 1

You could draw the background to the canvas once (with the paint enabled). Then you can save the canvas to a bitmap and from then on use that bitmap instead, avoiding the need for the paint.

It’s a bit of a crappy solution but it works. I’m guessing there is a better way to do this

background2 = Bitmap.createBitmap(width,height,Config.RGB_565);
Canvas c = new Canvas(background2);
c.drawBitmap(background, 0, 0, backgroundPaint);

then use background2 instead, and probably recycle() background.