Question

I have a scroll view, containing a view into which I place paired background color imageviews and image imageviews. I use this to present a simple scroll for my users to select an image to transfer to a main imageview display.

I have the scrollview background color set to light grey, alpha 0,5, the view set to clearcolor, alpha 1, opaque=true, the background color image set to either black or white, alpha 1, opaque = true and the image is set to alpha 1, opaque=true.

The issue I have is that within the app-info.plist, I have added “Renders with group opacity”, however regardless of the setting (yes or no), the background and image inherit the opacity of the scrollview.

In this image, you can see the main image in the background.
The light grey area is the scrollview, opaque = true, background = light grey, alpha=0,9
On top is the UIView, opaque=true, background = clear, alpha =1
The dark area around the first thumb is my active image indicator, opaque = true, background = dark grey, alpha =1
The white area (not visible) around the other thumbs is my notactive indicator, opaque=true, background = white, alpha =1
The imageview containing the thumbs is opaque =true, background white, alpha =1

However, you can see the background image through the thumbs. I wish the thumbs to be fully opaque and the grey to be alpha 0,5. This current setting of 0,9 is being used simply because this is the best I can make it.

This image is taken with the group opacity set to no, however the image is identical with group opacity set to yes.

I have seen this done elsewhere on other apps, however apart from a simple statement about what this parameters does,I cannot find simple instructions on how to implement this, as how I am doing must surely be wrong.

Any advice is welcome.

Regards
Chris H

Answer 1

This is a fairly common issue because people don’t anticipate that setting the alpha on a view will affect the rendering of the subviews. In your case this will be extremely easy to fix since you only want your background color to not be opaque. You can easily set a background color’s alpha and it will not affect the view’s subviews.

First set all of your views alphas to 1.0.

Second set the gray background color’s opacity to 0.5. You can do this in code creating a color like:

[[UIColor darkGrayColor] colorWithAlphaComponent:0.5]

or in IB by clicking the background color in the inspector and adjusting the opacity slider in the color picker: