Black artifacts on snapshot canvas mode with alpha texture

Audio and Graphics
#1

Hi everybody, today I’m trying to make a simple painting app and I found some interesting code on the corona blog:

local w = display.viewableContentWidth local h = display.viewableContentHeight local bg = display.newRect(0,0,w,h) bg.anchorX = 0 bg.anchorY = 0 local snapshot = display.newSnapshot(w,h) snapshot:translate(w\*0.5, h\*0.5) snapshot.canvasMode = "discard" function listener(event) local x,y = event.x - snapshot.x, event.y - snapshot.y if event.phase == "began" or event.phase == "moved" then local o = display.newImage("brush.png", x, y) o:setFillColor(1,0,0) snapshot.canvas:insert( o ) snapshot:invalidate("canvas") end end Runtime:addEventListener("touch", listener)

This sample is working nicely on the simulator but when I build it on my android device (galaxy s7) there are black artifacts all around my brush when I try to draw slowly as you see in the screenshot linked on this post.

While I concede this is an interesting effect it is very annoying for the goal of my app.

Do you know how I can fix this issue?

I’ve linked everything in the post to reproduce this bug.

#2

I changed the texture of my brush removing alpha nuance and it removes the black contouring, but I really want the anti-aliasing around my circle. Any idea of what is happening?

#3

Try setting up high-precision shaders in your config.lua: https://docs.coronalabs.com/guide/basics/configSettings/index.html#shader-precision

#4

I changed the texture of my brush removing alpha nuance and it removes the black contouring, but I really want the anti-aliasing around my circle. Any idea of what is happening?

#5

Try setting up high-precision shaders in your config.lua: https://docs.coronalabs.com/guide/basics/configSettings/index.html#shader-precision