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iPhone 中高效的缩略图创建

发布于 2024-09-05 14:46:24 字数 39 浏览 5 评论 0原文

在 iPhone 中从任意网页图像创建缩略图的最有效方法是什么？

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幻想少年梦 2024-09-12 14:46:24

两种快速创建图像缩略图方法的比较
请参阅此链接了解详细信息
http://www.cocoaintheshell.com/2011/01/uiimage-scaling-图像/
或者
http://vocaro.com/ trevor/blog/2009/10/12/resize-a-uiimage-the-right-way/

对于未来，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];
}

结果长凳给了我以下内容：

Time Profiler：4233ms
Live bytes：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：

Time Profiler：3433ms
Live bytes：681Kb
使用的总字节数: 77.63Mb

您可以看到使用 ImageIO 比 UIKit 快约 19%，并且使用的内存也略少。

the comparison of two method for fast creating thumbnail from image
kindly see this link for detail
http://www.cocoaintheshell.com/2011/01/uiimage-scaling-imageio/
or
http://vocaro.com/trevor/blog/2009/10/12/resize-a-uiimage-the-right-way/

for future , just copy pasting code from first one

First method, using 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];
}

Results of the benches gave me the following :

Time Profiler : 4233ms
Live bytes : 695Kb
Overall bytes used : 78.96Mb

Second method, using 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);
    }

he benches gave me this :