Saving a Quartz Context to the Camera Roll. How do I do it? :)

[kzad]

I made a little program to sketch with fingers, just for getting to know the sdk. How can I insert functionality to save the sketch to the camera roll?

Thanks.

[RickMaddy]

Do a search here on 'UIImageWriteToSavedPhotosAlbum' and you will find code that does what you need.

[kzad]

Great, this is exactly what I needed. For anyone else viewing this post, if you draw using quartz you can create a UIImage from a CGImageRef with

- (id)initWithCGImage: (CGImageRef)CGImage

[kzad]

hmm, is there any problem with calling this function in the iphone simulator?

probably i'm doing something wrong though, when i try to call the funciton like this:

UIImage *toSave = [[UIImage alloc] initWithContentsOfFile:@"pic.png"];
UIImageWriteToSavedPhotosAlbum(toSave, nil, nil, nil);

my program crashed with the following stack:



any suggestions?

[SkylarEC]

I'd probably go with something like this (simplified, yes, but it covers what you need to do).

UIGraphicsBeginImageContext(self.view.frame.size);
/*Draw your image into your context here */

UIImageWriteToSavedPhotosAlbum(UIGraphicsGetImageFromCurrentImageContext(), nil, nil, nil); 
UIGraphicsEndImageContext();

To fix your current issue though, try:

//If the image is within the root of your app.
[UIImage alloc imageNamed:@"pic.png"]; 

//Or, if it isn't in the root but is still within the app bundle: ie /My.app/Images
[UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"pic" ofType:@"png"]]];

//Or, if the image is in your Documents directory
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *pathToYourImage = [NSString pathWithComponents:[NSArray arrayWithObjects:documentsDirectory, @"pic.png", nil]];
[UIImage imageWithContentsOfFile:pathToYourImage];

[kzad]

Thanks a lot for your help. For various reasons I couldn't implement it exactly like you suggested, what I did do in the end was something like this:

toSave = [[UIImage alloc] initWithCGImage:
CGBitmapContextCreateImage(_myContext);];

Later I save it to the album.

This works but for two problems, which you might be able to help me with:

1. The images are saved "mirrored" on the horizontal axis. It's pretty weird, like 'v' would become '^'.

2. The thumbnails in the photoalbum are solid black, no matter what I draw.

Any suggestions?

[SkylarEC]

I don't know about the black thumbnail. The image is flipped because the CoreGraphics drawing surface' y axis is correct, and UIKit's y axis is inverted (for some weird reason). You will need to translate the grid and scale the image accordingly. Use these two lines:

	CGContextTranslateCTM(UIGraphicsGetCurrentContext, 0.0, CGImageGetHeight(theImage));  //Whereas theImage is a CGImageRef.  Using that is much more accurate than feeding in a height variable, but if you must, use a CGFloat variable.
	CGContextScaleCTM(UIGraphicsGetCurrentContext, 1.0, -1.0);

[kzad]

I'm running the following code when saving:

CGContextTranslateCTM(_myContext, 1, -1);
CGContextScaleCTM(_myContext, 0, 480); //the image is the whole screen
CGImageRef temp = CGBitmapContextCreateImage(_myContext);

but this code doesn't have any effect, it gets saved just as before, mirror flipped, and what's more - i played with the translate and scaling parameters and it looks like they're not doing anything.

i'm at a loss. help would be greatly appreciated.

[kzad]

I finally solved everything like this:

UIGraphicsBeginImageContext(self.window.bounds.siz e);
[self.window.layer renderInContext:UIGraphicsGetCurrentContext()];
toSave = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

takes care of the inversion problem and the thumbnails without a need for scaling.