spectogram-prototype/SpectogramPrototype/Spectographer.m

//
//  Spectographer.m
//  SpectogramPrototype
//
//  Created by Joshua Moerman on 29/12/13.
//  Copyright (c) 2013 Joshua Moerman. All rights reserved.
//

#import "Spectographer.h"
#import "FFTTest.h"
#import "AudioFile.h"

uint8_t clamp_to_uint8(float x){
	if(x >= 1.0) return 255;
	if(x <= 0.0) return 0;
	return (uint8_t)(255.0f * x);
}

@interface Spectographer (){
	FFTTest * FFTHandler;
	AudioFile * audioFile;
    NSUInteger sample;
	float * left;
	float * right;
}
- (void)threadTask:(void (^)(CGImageRef))callback;
- (CGImageRef)singleStep CF_RETURNS_RETAINED;
@end

@implementation Spectographer

- (id)init{
	if(self = [super init]){
		FFTHandler = [[FFTTest alloc] init];
        sample = 0;
		left = calloc(FFTHandler.acceptedSize, sizeof(float));
		right = calloc(FFTHandler.acceptedSize, sizeof(float));
	}
	return self;
}

- (void)openAudioFile:(NSURL *)url{
	audioFile = [AudioFile audioFileFromURL: url];
	assert(audioFile);
}

- (void)generate:(void (^)(CGImageRef))callback{
	[NSThread detachNewThreadSelector:@selector(threadTask:) toTarget:self withObject:callback];
}

- (void)threadTask:(void (^)(CGImageRef))callback{
	CGImageRef cgImage = nil;
	while((cgImage = [self singleStep])){
		callback(cgImage);
		CGImageRelease(cgImage);
	}
}

- (CGImageRef)singleStep{
	unsigned int size = FFTHandler.acceptedSize;
	unsigned int width = 128;
	unsigned int height = size/8;
	
	uint8_t * rgba = calloc(width*height*4, sizeof(uint8_t));
	
	unsigned int x = 0;
	for(; x < width; ++x){
		if(![audioFile fillLeft:left andRight:right forRange:NSMakeRange(sample, size)])
			break;
		[FFTHandler inPlaceFFT:left forSize:size];
		[FFTHandler inPlaceFFT:right forSize:size];
		for(unsigned int y = 0; y < height; ++y){
			unsigned int yy = height - y - 1;
			rgba[4*width*yy + 4*x + 0] = clamp_to_uint8(100.0f * left[y]);
			rgba[4*width*yy + 4*x + 1] = clamp_to_uint8(100.0f * right[y]);
			rgba[4*width*yy + 4*x + 2] = clamp_to_uint8(10.0f * (left[y] + right[y]));
			rgba[4*width*yy + 4*x + 3] = 0;
		}
        sample += size / 8;
	}
	if(!x){
		free(rgba);
		return nil;
	}
	
	CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
	assert(colorSpace);
	CGContextRef bitmapContext = CGBitmapContextCreate(rgba, width, height, 8, 4*width, colorSpace, (CGBitmapInfo)kCGImageAlphaNoneSkipLast);
	assert(bitmapContext);
	CGImageRef cgImage = CGBitmapContextCreateImage(bitmapContext);
	assert(cgImage);
	
	CGContextRelease(bitmapContext);
	CGColorSpaceRelease(colorSpace);
	free(rgba);
	
	return cgImage;
}

@end