Saving UIImage as a PNG with an Alpha Channel (with transparency) on iOS

Say you let your user draw thing and let them go wild with their imaginations, as they probably create awesome drawings, you should probably want to save these images to somewhere.

After this short happy talk, here is the code snippet that saves your UIImage to the Documents folder with its alpha channel, if there is one. The other method is for reading that image back to an UIImage instance.

-(void)saveImageToDocs:(NSString *)fileName
{
	NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
	NSString *documentsDirectory = [paths objectAtIndex:0];
	NSString *filePath2 = [NSString stringWithFormat:@"%@/%@.png", documentsDirectory, fileName];

	// If you use this method, the transparency will be lost
	//NSData* imageData = UIImageJPEGRepresentation(drawImage.image, 1.0);
	//NSData* imageData = UIImagePNGRepresentation(drawImage.image);
	//[imageData writeToFile:filePath2 atomically:NO];

	// So use this one
	[UIImagePNGRepresentation(myUIImage) writeToFile:filePath2 atomically:YES];
}

-(void)loadImageFromDocs:(NSString *)fileName
{
	NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
	NSString *documentsDirectory = [paths objectAtIndex:0];
	NSString *filePath2 = [NSString stringWithFormat:@"%@/%@.png", documentsDirectory, fileName];
	if([[NSFileManager defaultManager] fileExistsAtPath:filePath2])
	{
		NSLog(@"image file exists");
		myUIImage = [UIImage imageWithContentsOfFile: filePath2];
	}
}