CoreGraphics图像调整大小 [英] CoreGraphics Image resize

问题描述

此代码来自Apple的WWDC 2011 Session 318 - iOS Performance in Depth，并使用CoreGraphics从服务器托管的图像创建缩略图。

This code is from Apple's WWDC 2011 Session 318 - iOS Performance in Depth and uses CoreGraphics to create thumbnails from server hosted images.

CGImageSourceRef src = CGImageSourceCreateWithURL(url);
NSDictionary *options = (CFDictionaryRef)[NSDictionary 
dictionaryWithObject:[NSNumber numberWithInt:1024
forKey:(id)kCGImageSourceThumbnailMaxPixelSize];

CGImageRef thumbnail = CGImageSourceCreateThumbnailAtIndex(src,0,options);
UIImage *image = [UIImage imageWithCGImage:thumbnail];
CGImageRelease(thumbnail);
CGImageSourceRelease(src); 

但它不起作用且文档没有真正帮助。在 iOS 文档 CGImageSource CGImageSourceRef CGImageSourceCreateThumbnailAtIndex 可用

But it doesnt work and the docs don't really help. In the iOS docs CGImageSource CGImageSourceRef CGImageSourceCreateThumbnailAtIndex are available

在Mac OS X v10.4或更高版本中

in Mac OS X v10.4 or later

我怎样才能让它发挥作用？

How can I get this to work?

编辑

这些是我得到的编译器错误：

These are the compiler errors I'm getting:

• 使用未声明的标识符'CGImageSourceRef'


• 使用未声明的标识符'kCGImageSourceThumbnailMaxPixelSize'


• 使用未声明的标识符'src'


• 函数'CGImageSourceCreateThumbnailAtIndex'的隐式声明无效in C99


• 函数'CGImageSourceRelease'的隐式声明在C99中无效


• 函数'CGImageSourceCreateWithURL'的隐式声明在C99中无效

• Use of undeclared identifier 'CGImageSourceRef'
• Use of undeclared identifier 'kCGImageSourceThumbnailMaxPixelSize'
• Use of undeclared identifier 'src'
• Implicit declaration of function 'CGImageSourceCreateThumbnailAtIndex' is invalid in C99
• Implicit declaration of function 'CGImageSourceRelease' is invalid in C99
• Implicit declaration of function 'CGImageSourceCreateWithURL' is invalid in C99

推荐答案

男生错误。

未添加 #import< ImageIO / ImageIO.h>

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