Command line Cocoa program which overlays a png over another image - great for image banners on app icons

main.m

//
//  ImageMerger
//
//  Created by Cardasis, Jonathan (J.) on 4/15/16.
//  Copyright © 2016 Cardasis, Jonathan (J.). All rights reserved.
//

#import <Foundation/Foundation.h>
#import <Cocoa/Cocoa.h>

NSImage* mergeImages(NSImage *bottom, NSImage *overlay, CGFloat overlayAlpha){
    NSImage *newImage = [[NSImage alloc] initWithSize:[bottom size]];
    [newImage lockFocus];
    
    CGRect newImageRect = CGRectZero;
    newImageRect.size = [newImage size];
    
    [bottom drawInRect:newImageRect];
    if(overlayAlpha < 1){
        [overlay drawInRect:newImageRect fromRect:NSZeroRect operation:NSCompositeSourceOver fraction:overlayAlpha];//draw with opacity
    }else{
        [overlay drawInRect:newImageRect];
    }
    
    [newImage unlockFocus];
    
    return newImage;
}


bool saveImageToFilepath(NSImage *image, NSString *path){
    CGImageRef imgRef = [image CGImageForProposedRect:NULL context:nil hints:nil];
    NSBitmapImageRep *imgRep = [[NSBitmapImageRep alloc] initWithCGImage:imgRef];
    NSData *imgData = [imgRep representationUsingType:NSPNGFileType properties:@{}];
    
    return [imgData writeToFile:path atomically:YES];
}


void printUsage(const char *appname){
    fprintf(stderr, "Proper Usage:\n");
    fprintf(stderr, "\t%s /path/to/oldAppIcon.png /path/to/overlayImage.png \n", appname);
}




//setIconBadge oldImg.png overlayImg.png
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        if(argc != 3){//2 arguments
            NSString *argZero = [NSString stringWithFormat:@"%s", argv[0]];
            const char *appname = [[[argZero lastPathComponent] stringByDeletingPathExtension] cStringUsingEncoding:NSUTF8StringEncoding];
            printUsage(appname);
            return 1;
        }
        
        NSArray *arguments = [[NSProcessInfo processInfo] arguments];
//        NSFileManager *fileManager = [[NSFileManager alloc] init];
//        NSString *currentPath =  [fileManager currentDirectoryPath];
        
        NSString *oldIconFilepath = arguments[1];
        NSString *overlayFilepath = arguments[2];
        

        NSImage *base = [[NSImage alloc] initByReferencingFile:oldIconFilepath];
        NSImage *overlay = [[NSImage alloc] initByReferencingFile:overlayFilepath];
        
        
        NSImage *finalIcon = mergeImages(base, overlay, 1.0);
        
        bool success = saveImageToFilepath(finalIcon, oldIconFilepath);//save over old app icon
        if(!success){
            fprintf(stderr, "A problem occured replacing the app icons.\n");
        }
    }
    return 0;
}