UIImage+ImmediateLoading.h

//
//  UIImage+ImmediateLoading.h
//  Code taken from https://gist.github.com/259357
//

#import <Foundation/Foundation.h>

@interface UIImage (UIImage_ImmediateLoading)

- (UIImage*) initImmediateLoadWithContentsOfFile:(NSString*)path;
+ (UIImage*)imageImmediateLoadWithContentsOfFile:(NSString*)path;

@end

UIImage+ImmediateLoading.m

//
//  UIImage+ImmediateLoading.h
//  Code taken from https://gist.github.com/259357
//

#import "UIImage+ImmediateLoading.h"

@implementation UIImage (UIImage_ImmediateLoading)

+ (UIImage*)imageImmediateLoadWithContentsOfFile:(NSString*)path {
    return [[UIImage alloc] initImmediateLoadWithContentsOfFile: path] ;
}

- (UIImage*) initImmediateLoadWithContentsOfFile:(NSString*)path {
    UIImage *image = [[UIImage alloc] initWithContentsOfFile:path];
    if(!image) return nil;

    CGImageRef imageRef = [image CGImage];
    CGColorSpaceRef gray = CGColorSpaceCreateDeviceGray();
    CGColorSpaceRef colorSpace = CGImageGetColorSpace(imageRef);
    //Stack Overflow and this original gist tell us kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Little
    // is required for the work to stay off the main thread but we can't source this
    //Considering you can't create a bitmap context for a grayscale with those flags,
    //we'll take out chances this way
    CGBitmapInfo info;
    if (colorSpace == gray) {
        info = kCGImageAlphaNone;
    } else {
        info = kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Little;
    }
    CGColorSpaceRelease(gray);
    CGRect rect = CGRectMake(0.f, 0.f, CGImageGetWidth(imageRef), CGImageGetHeight(imageRef));
    CGContextRef bitmapContext = CGBitmapContextCreate(NULL,
                                                       rect.size.width,
                                                       rect.size.height,
                                                       CGImageGetBitsPerComponent(imageRef),
                                                       CGImageGetBytesPerRow(imageRef),
                                                       colorSpace,
                                                       info
                                                       );

    CGContextDrawImage(bitmapContext, rect, imageRef);
    CGImageRef decompressedImageRef = CGBitmapContextCreateImage(bitmapContext);
    UIImage* decompressedImage = [[UIImage alloc] initWithCGImage: decompressedImageRef];
    CGImageRelease(decompressedImageRef);
    CGContextRelease(bitmapContext);

    return decompressedImage;
}

@end