PNG with pre-existing alpha appears to be reset to alpha=1 when added to a display group

brianmacdiarmuide · January 24, 2017, 6:12pm

Hi

I have a game scene with 3 main display groups. In the back group, I want 3 layers of png images one on top of the other to ultimately create a parallax starfield effect. They have decreasing alpha. The first one added is opaque, the next layer is at 80% alpha, the top layer is 60%. However, when I add these layers, only the top one is visible… as if the alpha is set to 1 again on at least the top image ( They all still have the right alpha when opened in Gimp, or a basic image viewer ). I know I can set the alpha with

object.alpha&nbsp;

I have been able to achieve the desired effect in the lua code by changing the alpha

… but I was wondering why this is happening?

I’ve been adding the layers to the

backGroup

like this:

parallaxBack = display.newImageRect( &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; backGroup, "parallax/Parallax100.png", &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; display.contentWidth, display.contentHeight ) &nbsp;&nbsp;&nbsp; parallaxBack.x = display.contentCenterX &nbsp;&nbsp;&nbsp; parallaxBack.y = display.contentCenterY &nbsp;&nbsp;&nbsp; parallaxMid = display.newImageRect( &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; backGroup, "parallax/Parallax80.png", &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; display.contentWidth, display.contentHeight ) &nbsp;&nbsp;&nbsp; parallaxMid.x = display.contentCenterX &nbsp;&nbsp;&nbsp; parallaxMid.y = display.contentCenterY &nbsp;&nbsp;&nbsp; parallaxFront = display.newImageRect( &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; backGroup, "parallax/Parallax60.png", &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; display.contentWidth, display.contentHeight ) &nbsp;&nbsp;&nbsp; parallaxFront.x = display.contentCenterX &nbsp;&nbsp;&nbsp; parallaxFront.y = display.contentCenterY