CODEWITHSUNDEEP
iphonecocoa-touchimagetransparency
ragnarius
ragnarius

Reputation: 5813

Transparent color works on the simulator but becomes black on the iPhone

I am trying to draw an image that has some transparent regions. I load the image using 

image = [UIImage imageNamed:@"testimage.png"];

and draw it using

[image drawAtPoint:CGPointMake(0,0)];

The UIView on which I draw the image is not opaque (and it has a transparent background color).

The problem is that everything works fine on the simulator, but when I run the app on my iPhone the transparent color becomes black! Can anyone pinpoint my error?

Upvotes: 3

Views: 4177

Answers (3)

Austin
Austin

Reputation: 449

The correct answer to this problem is the .PNG format you are saving your image with. If you save as PNG-8, you will run into this problem more often that not, since it only supports 1 transparent color. If you open your .PNG file and then re-save it as a 24-bit format, you will gain genuine transparency.

Reference this thread for discussion and clarification.

  • EDIT: Just to be clear, .PNG does not have an 'alpha channel', so Chris' answer is misleading. Just be sure to save in 24-bit format with transparency enabled.

Upvotes: 2

ragnarius
ragnarius

Reputation: 5813

I solved my problem by loading it into colorsync and then saving it.

Upvotes: 0

Chris
Chris

Reputation: 748

I had the same problem today with a picture of mine. I've created the picture my self in GraphicConverter.

My solution was to add an alpha channel to the picture. I did this with GraphicConverter using the command found in Picture => Alpha Channel => Create Alpha Channel with transparency . It could be that the command has a different name for you as I use the app with a german language setting.

Hope this helps.

Upvotes: 3

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