How do you load a local jpeg or png image file into an iPhone app?

Question

Or I should ask why is it so difficult for me? The answer is probably that I'm new to iPhone development and I'm trying to ditch my old methods and step into the new platform of the future. From start to finish, I have a few questions about this process...

1. If I create a .png image, where does it go in my project's directory (i.e. my computer's hard drive)? Can I put it anywhere on my hard drive and Xcode will copy it in the right place when I load it into Xcode?
2. Once it exists on my hard drive somewhere, how do I add it to my Xcode project? Can I just drag the file into any folder in the "Groups & Files" tree?
3. Once I drag it into Xcode, what copy settings do I want to use in that copy file dialog box that pops up? Copy items into destination group's folder checkbox? Reference Type? Recursively create groups for added folders?
4. Once the .png image has properly been added to my project, what's the easiest way to get it into an CGImageRef? The documentation shows an example using the CGImageCreateWithPNGDataProvider helper method, but says it's not supported by the iOS SDK. I'd like to use the CGImageRef for repeatedly drawing the image to a bitmap context.

Thanks so much in advance and I apologize for the lengthy question, I'm just surprised it's such a convoluted process compared to some other platforms.

Answer 1

Hi there,

1 & 2) You can place it anywhere on your harddrive (so long as you don't move or delete it.. then you'll need to update the reference in XCode). Within XCode, you may want to create a "Group" for your images by right clicking in the left model tree and selecting it from the menu. Then just right click again and goto "Add" -> "Existing files or folders" and select the png file. If you accidentally add it in the wrong group, you can drag it around in XCode model tree. You can also drag and drop the file into a group in XCode from the Finder window.

3) You can just use "Default" copy settings and you don't need to copy it into the project. A reference is good enough and no need to recursively create groups.

4) What are you trying to do with the image? Do you need a CGImageRef from the png file or could you use an UIImageView or UIImage to load it from the file, or you can just lay it out in Interface Builder (IB). If you elaborate a little bit more about how you are using the image, maybe we can help you.

Answer 2

1) It can go anywhere in Groups & Files, but if you only have a few, I'd recommend sticking it into the Resources groups. Remember, the groups in Groups & Files don't match actual folders in your directory structure however. They simply exist to organize your files.

2) Just drag it into the Groups & Files pane.

3) I'd use the 'copy' option. Not copying it is often useful when you're linking to shared resources used by different projects.

4) I haven't used CGImageRef myself, but if you just want a UIImage, you can simply call its imageNamed: class method and specify the image name without any additional paths leading up to it. It's assumed the file will be relative to your application's main bundle.

Answer 3

If you have a particular image or set of images that you want included as part of the application, you can simply drag them into the project -- I prefer the Resources section for this -- and reference them by name using UIImage "imageNamed" for initialization.

If you are trying to load images that are local to an individual iPhone, that uses different techniques, but that doesn't seem to be what you are after.

I'm new to iPhone programming too, so I hope this helps.

Answer 4

If you load into UIImage, you can get a CGImageReg:

    UIImage *image = [UIImage imageNamed:@"image.png"];
CGImageRef imageRef = [image CGImage];