Log brightness of pixels in NSImage - objective-c

Question

My goal is to find the brightness of every pixel in an image and then append it into an array. I have looked online (since this is way outside of my comfort zone, but I figured that's how I'll learn), and found several examples that get the pixel colors in Swift for IOS using UIImage. Unfortunately the same code can't be used for OS X since NSImage doesn't seem to convert to CGImage the same way a UIImage does. So that code became next to useless for me. Next I found this site, which offers a piece of example code that finds and logs the brightness of each pixel in an image. Bingo! The only problem is it is in Objective C, which I only slightly understand. After a bit more failed searches, I began attempting to translate the Objective C code. This is the original code:
- (void)setupWithImage:(UIImage*)image {
UIImage * fixedImage = [image imageWithFixedOrientation];
self.workingImage = fixedImage;
self.mainImageView.image = fixedImage;
// Commence with processing!
[self logPixelsOfImage:fixedImage];
}
- (void)logPixelsOfImage:(UIImage*)image {
// 1. Get pixels of image
CGImageRef inputCGImage = [image CGImage];
NSUInteger width = CGImageGetWidth(inputCGImage);
NSUInteger height = CGImageGetHeight(inputCGImage);
NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * width;
NSUInteger bitsPerComponent = 8;
UInt32 * pixels;
pixels = (UInt32 *) calloc(height * width, sizeof(UInt32));
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(pixels, width, height,
bitsPerComponent, bytesPerRow, colorSpace,
kCGImageAlphaPremultipliedLast|kCGBitmapByteOrder32Big);
CGContextDrawImage(context, CGRectMake(0, 0, width, height), inputCGImage);
CGColorSpaceRelease(colorSpace);
CGContextRelease(context);
#define Mask8(x) ( (x) & 0xFF )
#define R(x) ( Mask8(x) )
#define G(x) ( Mask8(x >> 8 ) )
#define B(x) ( Mask8(x >> 16) )
// 2. Iterate and log!
NSLog(#"Brightness of image:");
UInt32 * currentPixel = pixels;
for (NSUInteger j = 0; j < height; j++) {
for (NSUInteger i = 0; i < width; i++) {
UInt32 color = *currentPixel;
printf("%3.0f ", (R(color)+G(color)+B(color))/3.0);
currentPixel++;
}
printf("\n");
}
free(pixels);
#undef R
#undef G
#undef B
}
And this is my translated code:
func logPixelsOfImage(image: NSImage) {
var inputCGImage: CGImageRef = image
var width: UInt = CGImageGetWidth(inputCGImage)
var height: UInt = CGImageGetHeight(inputCGImage)
var bytesPerPixel: UInt = 4
var bytesPerRow: UInt = bytesPerPixel * width
var bitsPerComponent: UInt = 8
var pixels: UInt32!
//pixels = (UInt32 *) calloc(height * width, sizeof(UInt32));
var colorSpace: CGColorSpaceRef = CGColorSpaceCreateDeviceRGB()
var context: CGContextRef = CGBitmapContextCreate(pixels, width, height, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big) //Error: Use of unresolved identifier 'kCGImageAlphaPremultipliedLast' Second Error: Use of unresolved identifier 'kCGBitmapByteOrder32Big'
CGContextDrawImage(context, CGRectMake(0, 0, width, height), inputCGImage) // Error: 'Uint' is not convertible to 'CGFloat'
/*
#define Mask8(x) ( (x) & 0xFF )
#define R(x) ( Mask8(x) )
#define G(x) ( Mask8(x >> 8 ) )
#define B(x) ( Mask8(x >> 16) )
*/
println("Brightness of image:")
var currentPixel: UInt32 = pixels
for (var j : UInt = 0; j < height; j++) {
for ( var i : UInt = 0; i < width; i++) {
var color: UInt32 = currentPixel
//printf("%3.0f ", (R(color)+G(color)+B(color))/3.0);
currentPixel++
}
println("/n")
}
//free(pixels)
/*
#undef R
#undef G
#undeg B
*/
}
Comments contain (a) errors that the code provides or (b) code that was in the original that I don't know how to translate.
So what's my question?
Is there a better way of finding the brightness of a pixel than what is shown in the Objective-C code? If so, how would you do that? If not, how would I go about finishing up the translation of the original code?
Thanks -- A CodeIt that is extremely confused and every so slightly desperate.