在Android中可绘制半透明图形，但边缘黑

Question

I have the below image (the white bubble in the image) to draw in a canvas. When I draw the image using the code.., the image 's edge is getting black circle and rounded .. the edge's alpha is 0x00.

image.setBounds(left, top, right, bottom);

image.draw(canvas);

Expected When I draw

How could I remove the black circle??? Is the image wrong?? or Anyone know the clue, Please give me a clue.. Thanks in advance..

^^

Answer 1

Is your expected output taken from an image editor (Photoshop?) If so, that'll be the result of a 32-bit blend, whereas it looks like the alpha-blend on Android is being performed in 16-bits, hence the banding in the background, and halo around your image.

Presuming you're using Bitmap objects, you can check whether this is the case by calling bitmap.getConfig() to find their colour depth (from the Bitmap.Config enum).

Edit : One more thing that may be causing the halo - you say the edges of your sprite have an alpha of 0, but what about the RGB values? Make sure the ARGB is set to full-white (ARGB 0x00ffffff) rather than black (ARGB 0x00000000).