/*

     File: Texture.m

 Abstract:  A help class that loads an OpenGL texture from an image path.

  Version: 1.1

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*/

#import "Texture.h"

#import <OpenGL/glu.h>

#define TEXTURE_WIDTH       1024

#define TEXTURE_HEIGHT      512

@interface Texture (PrivateMethods)

- (BOOL) getImageDataFromPath:(NSString*)path;

- (void) loadTexture;

@end

@implementation Texture

- (id) initWithPath:(NSString*)path

{   

    if (self = [super init]) {

        if ([self getImageDataFromPath:path])

            [self loadTexture];

    }

    return self;

}

- (GLuint) textureName

{

    return texId;

}

- (BOOL) getImageDataFromPath:(NSString*)path

{

    NSUInteger              width, height;

    NSURL                   *url = nil;

    CGImageSourceRef        src;

    CGImageRef              image;

    CGContextRef            context = nil;

    CGColorSpaceRef         colorSpace;

    data = (GLubyte*) calloc(TEXTURE_WIDTH * TEXTURE_HEIGHT * 4, sizeof(GLubyte));

    url = [NSURL fileURLWithPath: path];

    src = CGImageSourceCreateWithURL((CFURLRef)url, NULL);

    if (!src) {

        NSLog(@"No image");

        free(data);

        return NO;

    }

    image = CGImageSourceCreateImageAtIndex(src, 0, NULL);

    CFRelease(src);

    width = CGImageGetWidth(image);

    height = CGImageGetHeight(image);

    colorSpace = CGColorSpaceCreateDeviceRGB();

    context = CGBitmapContextCreate(data, width, height, 8, 4 * width, colorSpace, kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Host);

    CGColorSpaceRelease(colorSpace);

    // Core Graphics referential is upside-down compared to OpenGL referential

    // Flip the Core Graphics context here

    // An alternative is to use flipped OpenGL texture coordinates when drawing textures

    CGContextTranslateCTM(context, 0.0, height);

    CGContextScaleCTM(context, 1.0, -1.0);

    // Set the blend mode to copy before drawing since the previous contents of memory aren't used. This avoids unnecessary blending.

    CGContextSetBlendMode(context, kCGBlendModeCopy);

    CGContextDrawImage(context, CGRectMake(0, 0, width, height), image);

    CGContextRelease(context);

    CGImageRelease(image);

    return YES;

}

- (void) loadTexture

{

    glGenTextures(1, &texId);

    glGenBuffers(1, &pboId);

    // Bind the texture

    glBindTexture(GL_TEXTURE_2D, texId);

    // Bind the PBO

    glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pboId);

    // Upload the texture data to the PBO

    glBufferData(GL_PIXEL_UNPACK_BUFFER, TEXTURE_WIDTH * TEXTURE_HEIGHT * 4 * sizeof(GLubyte), data, GL_STATIC_DRAW);

    // Setup texture parameters

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);

    // OpenGL likes the GL_BGRA + GL_UNSIGNED_INT_8_8_8_8_REV combination

    // Use offset instead of pointer to indictate that we want to use data copied from a PBO        

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, TEXTURE_WIDTH, TEXTURE_HEIGHT, 0, 

                 GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, 0);

    // We can delete the application copy of the texture data now

    free(data);

    glBindTexture(GL_TEXTURE_2D, 0);

    glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);

}

- (void) dealloc

{

    glDeleteTextures(1, &texId);

    glDeleteBuffers(1, &pboId);

    [super dealloc];

}

@end