I was on the same boat a few weeks ago and I wanted to ask something similar but I completely forgot.
I was trying to mask an image with a mask image created from a bezier path, the idea was that I created my bezier path then I fill EO the path so the part that was supposed to mask I left it of white color and the rest was black, then I created an image from that path using the UIGpraphicContext methods. The image was created successfully, then I created the mask form that image passing the bits per row, etc, and when I apply the mask to the image I wanted to mask I left all fine expect the part that was supposed to mask (and leave transparent), this part was black. After checking everything and realizing all was ok, I desisted on using CG and used instead CALayer, I set the contents to the mask image and then CALayer has a mask method that seemed to work fine. But I really wanted to make it work with CG. :( Gustavo On Jun 27, 2011, at 1:03 AM, Luke Hiesterman wrote: > > > On Jun 26, 2011, at 3:06 PM, "James Miller" <jmiller3...@gmail.com> wrote: > >> I've been reading and experimenting and browsing and reading and >> experimenting but mostly failing miserably here and I need to ask the hive >> mind for some assistance. >> >> In a nutshell, I'm just trying to take a range of white colors out of a >> UIImage and make those colors transparent. From what I've read, I shouldn't >> use PNGs with an alpha already defined, but I also shouldn't use JPGs >> because they don't have an alpha channel. > > Where did you read that you shouldn't use PNGs with alpha? > >> >> So I've been trying to the extract the UIImage's CGImage and then convert it >> from RGB to RGBA and THEN mask it with CGImageCreateWithMaskingColors with >> no success (transparent areas appear as black). I've tried various >> techniques involving CGBitmapContextCreate and CGImageCreate but with no >> luck. > > Note that if you did successfully make parts of your image transparent, they > would show up as black if drawn into an opaque context. How are you > drawing/displaying the image? > > Luke > >> >> This can't POSSIBLY be as complicated as I'm making this out to be! Can >> someone please show me how to do this properly!? >> >> A thousand thank yous and a pet herring named after you! >> >> --James >> >> >> >> >> "The world is divided into people who do things and people who get the >> credit. Try, if you can, to belong to the first class. There's far less >> competition." >> >> _______________________________________________ >> >> Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) >> >> Please do not post admin requests or moderator comments to the list. >> Contact the moderators at cocoa-dev-admins(at)lists.apple.com >> >> Help/Unsubscribe/Update your Subscription: >> http://lists.apple.com/mailman/options/cocoa-dev/luketheh%40apple.com >> >> This email sent to luket...@apple.com > _______________________________________________ > > Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) > > Please do not post admin requests or moderator comments to the list. > Contact the moderators at cocoa-dev-admins(at)lists.apple.com > > Help/Unsubscribe/Update your Subscription: > http://lists.apple.com/mailman/options/cocoa-dev/gustavxcodepicora%40gmail.com > > This email sent to gustavxcodepic...@gmail.com _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
