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MakeThumbnailOperation.m
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/*
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.
("Apple") in consideration of your agreement to the following
terms, and your use, installation, modification or
redistribution of this Apple software constitutes acceptance of
these terms. If you do not agree with these terms, please do
not use, install, modify or redistribute this Apple software.
In consideration of your agreement to abide by the following
terms, and subject to these terms, Apple grants you a personal,
non-exclusive license, under Apple's copyrights in this
original Apple software (the "Apple Software"), to use,
reproduce, modify and redistribute the Apple Software, with or
without modifications, in source and/or binary forms; provided
that if you redistribute the Apple Software in its entirety and
without modifications, you must retain this notice and the
following text and disclaimers in all such redistributions of
the Apple Software. Neither the name, trademarks, service marks
or logos of Apple Inc. may be used to endorse or promote
products derived from the Apple Software without specific prior
written permission from Apple. Except as expressly stated in
this notice, no other rights or licenses, express or implied,
are granted by Apple herein, including but not limited to any
patent rights that may be infringed by your derivative works or
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
WITHOUT LIMITATION THE IMPLIED WARRANTIES OF NON-INFRINGEMENT,
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, REGARDING
THE APPLE SOFTWARE OR ITS USE AND OPERATION ALONE OR IN
COMBINATION WITH YOUR PRODUCTS.
IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT,
INCIDENTAL OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) ARISING IN ANY WAY
OUT OF THE USE, REPRODUCTION, MODIFICATION AND/OR DISTRIBUTION
OF THE APPLE SOFTWARE, HOWEVER CAUSED AND WHETHER UNDER THEORY
OF CONTRACT, TORT (INCLUDING NEGLIGENCE), STRICT LIABILITY OR
OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
*/
#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