Exporting Tutorial, the CG way

C4WorkSpace.m

//
//  C4WorkSpace.m
//  Exporting Tutorial
//
//  Created by Travis Kirton.
//

#import "C4WorkSpace.h"

@implementation C4WorkSpace {
    CGSize outputSize;

    CGContextRef imageContext;
    void *imageBuffer;
    size_t bitsPerComponent;
    size_t bitsPerPixel;
    size_t componentsPerPixel;
    size_t bytesPerRow;
}

-(void)setup {
    C4Font *font = [C4Font fontWithName:@"AvenirNextCondensed-Heavy" size:172];
    C4Shape *s = [C4Shape shapeFromString:@"DRAWING" withFont:font];
    s.backgroundColor = C4RED;
    s.center = self.canvas.center;
    [self.canvas addShape:s];

    imageContext = [self createImageContext];
    
    NSString *fileName = @"exportedImageFromC4.png";
    
    [self.canvas renderInContext:imageContext];
    [self saveImage:fileName];
}

-(CGContextRef)createImageContext {
    outputSize = self.canvas.frame.size;
    
    componentsPerPixel = 4;
    bytesPerRow = (size_t)outputSize.width * componentsPerPixel;
    bitsPerComponent = 8;
    bitsPerPixel = bitsPerComponent * componentsPerPixel;
    
    imageBuffer = malloc((size_t)outputSize.height * bytesPerRow);
    
    CGContextRef context = CGBitmapContextCreate(imageBuffer,
                                                 (size_t)outputSize.width,
                                                 (size_t)outputSize.height,
                                                 bitsPerComponent,
                                                 bytesPerRow,
                                                 CGColorSpaceCreateDeviceRGB(),
                                                 kCGImageAlphaPremultipliedFirst);
    CGAffineTransform invert = CGAffineTransformMake(1, 0, 0, -1, 0, outputSize.height);
    CGContextConcatCTM(context, invert);
    
    return context;
}

-(void)saveImage:(NSString *)fileName {
    CGDataProviderRef dataProvider = CGDataProviderCreateWithData(NULL,
                                                                  imageBuffer,
                                                                  bytesPerRow * (size_t)outputSize.height,
                                                                  NULL);
    CGImageRef imageRef = CGImageCreate((size_t)outputSize.width,
                                        (size_t)outputSize.height,
                                        bitsPerComponent,
                                        bitsPerPixel,
                                        bytesPerRow,
                                        CGColorSpaceCreateDeviceRGB(),
                                        kCGImageAlphaPremultipliedFirst,
                                        dataProvider,
                                        NULL,
                                        NO,
                                        kCGRenderingIntentDefault);
    UIImage *image = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    
    NSData *imageData = UIImagePNGRepresentation(image);
    image = nil;
    
    NSString *savePath = [[self documentsDirectory] stringByAppendingPathComponent:fileName];
    [imageData writeToFile:savePath atomically:YES];
}

-(NSString *)documentsDirectory {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    return paths[0];
}
@end