在iPhone中创建高效的缩略图

Question

在iPhone中从任意Web图像创建缩略图的最有效方法是什么？

Answer 1

从图像快速创建缩略图的两种方法的比较请看详细链接 http://www.cocoaintheshell.com/2011/01/uiimage-scaling-imageio/ 或 http://vocaro.com/trevor/blog/一十分之二千零九/ 12 /调整-A-UIImage的最右路/

为了将来,只需从第一个复制粘贴代码

第一种方法,使用UIKit

void)buildGallery
{
    for (NSUInteger i = 0; i < kMaxPictures; i++)
    {
        NSInteger imgTag = i + 1;
        NYXPictureView* v = [[NYXPictureView alloc] initWithFrame:(CGRect){.origin.x = x, .origin.y = y, .size = _thumbSize}];
        NSString* imgPath = [[NSBundle mainBundle] pathForResource:[NSString stringWithFormat:@"%d", imgTag] ofType:@"jpg"];
        UIImage* fullImage = [[UIImage alloc] initWithContentsOfFile:imgPath];
        [v setImage:[fullImage imageScaledToFitSize:_thumbSize]];
        [fullImage release];
}

长凳的结果给了我以下内容:

• 时间分析器:4233ms
• 实时字节:695Kb
• 使用的总字节数:78.96Mb

第二种方法,使用ImageIO

-(void)buildGallery
{
    for (NSUInteger i = 0; i < kMaxPictures; i++)
    {
        NSInteger imgTag = i + 1;
        NYXPictureView* v = [[NYXPictureView alloc] initWithFrame:(CGRect){.origin.x = x, .origin.y = y, .size = _thumbSize}];
        NSString* imgPath = [[NSBundle mainBundle] pathForResource:[NSString stringWithFormat:@"%d", imgTag] ofType:@"jpg"];
        CGImageSourceRef src = CGImageSourceCreateWithURL((CFURLRef)[NSURL fileURLWithPath:imgPath], NULL);
        CFDictionaryRef options = (CFDictionaryRef)[[NSDictionary alloc] initWithObjectsAndKeys:(id)kCFBooleanTrue, (id)kCGImageSourceCreateThumbnailWithTransform, (id)kCFBooleanTrue, (id)kCGImageSourceCreateThumbnailFromImageIfAbsent, (id)[NSNumber numberWithDouble:_maxSize], (id)kCGImageSourceThumbnailMaxPixelSize, nil];
        CGImageRef thumbnail = CGImageSourceCreateThumbnailAtIndex(src, 0, options); // Create scaled image
        CFRelease(options);
        CFRelease(src);
        UIImage* img = [[UIImage alloc] initWithCGImage:thumbnail];
        [v setImage:img];
        [img release];
        CGImageRelease(thumbnail);
    }

他长凳给了我这个:

• 时间分析器:3433ms
• 实时字节:681Kb
• 使用的总字节数:77.63Mb

您可以看到使用ImageIO比UIKit快约19%,并且使用的内存略少.

Answer 2

到目前为止，我发现适用于任何图像的唯一方法是将其显示在具有正确大小的 ImageView 中，然后从该视图创建位图。

但远非高效。