/*

    File:       MakeThumbnailOperation.m

    Contains:   An NSOperation subclass that creates a thumbnail from image data.

    Written by: DTS

    Copyright:  Copyright (c) 2010 Apple Inc. All Rights Reserved.

    Disclaimer: IMPORTANT: This Apple software is supplied to you by Apple Inc.

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                this notice, no other rights or licenses, express or implied,

                are granted by Apple herein, including but not limited to any

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                by other works in which the Apple Software may be incorporated.

                The Apple Software is provided by Apple on an "AS IS" basis. 

                APPLE MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING

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                THE APPLE SOFTWARE OR ITS USE AND OPERATION ALONE OR IN

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*/

#import "MakeThumbnailOperation.h"

@implementation MakeThumbnailOperation

- (id)initWithImageData:(NSData *)imageData MIMEType:(NSString *)MIMEType

    // See comment in header.

{

    assert(imageData != nil);

    assert(MIMEType != nil);

    self = [super init];

    if (self != nil) {

        self->_imageData = [imageData copy];

        self->_MIMEType  = [MIMEType  copy];

        self->_thumbnailSize = 32.0f;

    }

    return self;

}

- (void)dealloc

{

    CGImageRelease(self->_thumbnail);

    [self->_MIMEType release];

    [self->_imageData release];

    [super dealloc];

}

@synthesize imageData     = _imageData;

@synthesize MIMEType      = _MIMEType;

@synthesize thumbnailSize = _thumbnailSize;

@synthesize thumbnail     = _thumbnail;

- (void)main

{

    CGDataProviderRef   provider;

    CGImageRef          sourceImage;

    CGFloat             thumbnailSize;

    // Latch thumbnailSize for performance, and also to prevent it changing out from underneath us.

    thumbnailSize = self.thumbnailSize;

    assert(self.imageData != nil);

    assert(self.MIMEType != nil);

    // Set up the source CGImage.

    provider = CGDataProviderCreateWithCFData( (CFDataRef) self.imageData);

    assert(provider != NULL);

    if ( [self.MIMEType isEqual:@"image/jpeg"] ) {

        sourceImage = CGImageCreateWithJPEGDataProvider(provider, NULL, true, kCGRenderingIntentDefault);

    } else if ( [self.MIMEType isEqual:@"image/png"] ) {

        sourceImage =  CGImageCreateWithPNGDataProvider(provider, NULL, true, kCGRenderingIntentDefault);

    } else {

        sourceImage = NULL;

    }

    // Render it to a bitmap context and then create an image from that context.

    if (sourceImage != NULL) {

        static const CGFloat kWhite[4] = {0.0f, 0.0f, 0.0f, 1.0f};

        CGColorRef      white;

        CGContextRef    context;

        CGColorSpaceRef space;

        space = CGColorSpaceCreateDeviceRGB();

        assert(space != NULL);

        white = CGColorCreate(space, kWhite);

        assert(white != NULL);

        // Create the context that's thumbnailSize x thumbnailSize.

        context = CGBitmapContextCreate(NULL, thumbnailSize, thumbnailSize, 8, 0, space, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);

        if (context != NULL) {

            CGRect  r;

            // Make sure anything we don't cover comes out white.  While the next 

            // steps ensures that we cover the entire image, there's a possibility 

            // that we're dealing with a transparent PNG.

            CGContextSetFillColorWithColor(context, white);

            CGContextFillRect(context, CGRectMake(0.0f, 0.0f, thumbnailSize, thumbnailSize));

            // Calculate the drawing rectangle so that the image fills the entire 

            // thumbnail.  That is, for a tall image, we scale it so that the 

            // width matches thumbnailSize and the it's centred vertically.  

            // Similarly for a wide image.

            r = CGRectZero;

            r.size.width  = CGImageGetWidth(sourceImage);

            r.size.height = CGImageGetWidth(sourceImage);

            if (r.size.height > r.size.width) {

                // tall image

                r.size.height = (r.size.height / r.size.width) * thumbnailSize;

                r.size.width  = thumbnailSize;

                r.origin.y = - ((r.size.height - thumbnailSize) / 2);

            } else {

                // wide image

                r.size.width  = (r.size.width / r.size.height) * thumbnailSize;

                r.size.height = thumbnailSize;

                r.origin.x = - ((r.size.width - thumbnailSize) / 2);

            }

            // Draw the source image and get then create the thumbnail from the 

            // context. 

            CGContextDrawImage(context, r, sourceImage);

            self->_thumbnail = CGBitmapContextCreateImage(context);

            assert(self->_thumbnail != NULL);

        }

        CGContextRelease(context);

        CGColorSpaceRelease(space);

        CGColorRelease(white);

    }

    CGImageRelease(sourceImage);

    CGDataProviderRelease(provider);

}

@end