1.配置环境
- 工程引入SDWebImage开源库；
- 引入WebP.framework （demo中可以获得）
- 让SDWebImage支持WebP，设置如下Build Settings -- Preprocessor Macros , add SD_WEBP=1
2.用SDWebImage加载webp图片
//视图加载webp图片
UIView *webpView = [[UIView alloc] initWithFrame:CGRectMake(10, 80, 320, 100)];
webpView.backgroundColor = [UIColor yellowColor];
[self.view addSubview:webpView];
NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://mmbiz.qpic.cn/mmbiz_jpg/AZQZ9KUtamupibEQMmFDLqqsU7RLEvH5h5sPcyZEvhv6tQ5y3WAYKYibeQfnOtQulul5QHFHpL9b0icCKliajWFe2A/640?wx_fmt=jpeg&tp=webp&wxfrom=5&wx_lazy=1"]];
UIImageView *wpimage = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
#ifdef SD_WEBP
[wpimage setImage:[UIImage sd_imageWithWebPData:data]];
#endif
[webpView addSubview:wpimage];
3.Webview里加载webp图片
有两种方案：
1，和js协作。
2，自定义NSURLProtocal
和JS协作
webView 等网页上如果用的是 webP 图片,iOS 直接解析的话,会显示?图片.
？.png
实现方法：
- 在网页加载完成的回调里，截取到 HTML 及内部的 JS ,获取全部需要转码的 webP 格式图片下载地址。（调用 JS 预先准备好的方法，或者客户端一个一个的遍历也行).
- 在客户端本地开启线程下载图片,下载完成后,将图片转码由 webP—> png—>Base64(直接用 png/jpg 的话，不起没用)
- 将 Base64及原图片下载地址，对应调用 JS 准备好的方法进行替换
- 将下载后的图片进行缓存,并进行管理
注意点:
- 图片在最终显示成功前会显示成?,此处为了用户体验应该采用占位图片
- 图片显示成功前应该保持网页布局不调整,需要由 JS 预先设置好布局
- 图片在本地的缓存需要管理
例如，HTML的代码如下：
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
<title>webp</title>
<script type="text/javascript">
var YongChe = {}
YongChe.getAllWebPImg = function () {
var images = document.getElementsByTagName('img')
var srcList = []
var patt1 = new RegExp("\.webp$")
for (var i = 0; i < images.length; i++) {
if (patt1.test(images[i].src)) {
srcList.push(images[i].src)
}
}
return JSON.stringify(srcList)
}
YongChe.replaceWebPImg = function (src, localPath) {
elementList = document.querySelectorAll('img[src="' + src + '"]')
for (element in elementList) {
elementList[element].src = localPath
}
}
</script>
</head>
<body>
<img src="http://testing.yongche.org/images/150X1501.webp” width = 50 ,height = 20>
<script type="text/javascript">
console.log(YongChe.getAllWebPImg());
YongChe.replaceWebPImg('http://testing.yongche.org/images/logo.png','http://testing.yongche.org/images/150X1501.webp')
</script>
</body>
客户端代码如下：
- (void)webViewDidFinishLoad:(UIWebView *)webView{
//---------------------------------测试-----------------------------------
//获取`HTML`代码
NSString *lJs = @"document.documentElement.innerHTML";
NSString *str = [webView stringByEvaluatingJavaScriptFromString:lJs];
//执行约定好的方法,获取需要下载的 webp 图片
NSString *imgs = [webView stringByEvaluatingJavaScriptFromString:@"YongChe.getAllWebPImg();"];
NSArray *array = [NSJSONSerialization JSONObjectWithData:[imgs dataUsingEncoding:NSUTF8StringEncoding] options:0 error:nil];
_webpImageUrlDic = [NSMutableDictionary dictionaryWithCapacity:3];
for (NSString *imgUrl in array) {
//检查本地图片缓存
NSString *key = [[SDWebImageManager sharedManager] cacheKeyForURL:[NSURL URLWithString:imgUrl]];
NSString *localPath = [[SDImageCache sharedImageCache] defaultCachePathForKey:key];
NSString *newSrc = imgUrl;
BOOL localExsit = [[NSFileManager defaultManager] fileExistsAtPath:localPath];
if (localExsit) {
newSrc = [NSString stringWithFormat:@"file://%@", localPath];
}
//存储�webp图片和原图片，如果newSrc和webp相同则说明本地没有缓存图片
[_webpImageUrlDic setObject:imgUrl forKey:newSrc];
}
//处理webp格式加载
[_webpImageUrlDic enumerateKeysAndObjectsUsingBlock:^(id _Nonnull key, id _Nonnull obj, BOOL * _Nonnull stop) {
if([obj isEqualToString:key]){//说明这图没有缓存，还需要下载
[[SDWebImageDownloader sharedDownloader] downloadImageWithURL:[NSURL URLWithString:obj] options:0 progress:nil completed:^(UIImage *image, NSData *data, NSError *error, BOOL finished) {
if (image&&finished) {
NSString *js;
NSRange range = [[obj lowercaseString] rangeOfString:@".gif"];//检查是否是gif
BOOL isGif = (range.location != NSNotFound);
if (!isGif) {
[[SDImageCache sharedImageCache] storeImage:image forKey:obj];
NSString *base64 = [UIImageJPEGRepresentation(image,1) base64EncodedStringWithOptions:0];
js = [NSString stringWithFormat:@"YongChe.replaceWebPImg('%@','data:image/png;base64,%@')",obj,base64];
}else{//gif的图片如果直接存储，会变成jpg从而失去动画，因此要特殊处理
[[SDImageCache sharedImageCache] storeImage:image recalculateFromImage:false imageData:data forKey:obj toDisk:true];
NSString *base64 = [data base64EncodedStringWithOptions:0];
js = [NSString stringWithFormat:@"YongChe.replaceWebPImg('%@','data:image/gif;base64,%@')",obj,base64];
}
dispatch_async(dispatch_get_main_queue(), ^{
//更新UI操作
[self.webv stringByEvaluatingJavaScriptFromString:js];
});
}
}];
} else {
//缓存中存在，那么直接加载吧
NSString *js;
NSRange range = [[obj lowercaseString] rangeOfString:@".gif"];//检查是否是gif
NSData* data = [NSData dataWithContentsOfFile:[key stringByReplacingOccurrencesOfString:@"file://" withString:@""]];
NSString *base64 = [data base64EncodedStringWithOptions:0];
BOOL isGif = (range.location != NSNotFound);
if (!isGif) {
js = [NSString stringWithFormat:@"YongChe.replaceWebPImg('%@','data:image/png;base64,%@')",obj,base64];
}else{
js = [NSString stringWithFormat:@"YongChe.replaceWebPImg('%@','data:image/gif;base64,%@')",obj,base64];
}
dispatch_async(dispatch_get_main_queue(), ^{
//更新UI操作
[self.webv stringByEvaluatingJavaScriptFromString:js];
});
}
}];
}
效果如下：
和js协作.png
自定义NSURLProtocal
自定义CYCustomURLProtocal 继承自NSURLProtocal
#import <Foundation/Foundation.h>
@interface CYCustomURLProtocal : NSURLProtocol
@end
NSURLSession
#import "CYCustomURLProtocal.h"
#import "UIImage+WebP.h"
static NSString *URLProtocolHandledKey = @"URLHasHandle";
@interface CYCustomURLProtocal()<NSURLSessionDelegate,NSURLSessionDataDelegate>
@property (nonatomic,strong) NSURLSession *session;
@end
@implementation CYCustomURLProtocal
#pragma mark 初始化请求
+ (BOOL)canInitWithRequest:(NSURLRequest *)request
{
//只处理http和https请求
NSString *scheme = [[request URL] scheme];
NSString *extension = [[request URL] pathExtension];
if (([scheme caseInsensitiveCompare:@"http"] == NSOrderedSame || [scheme caseInsensitiveCompare:@"https"] == NSOrderedSame) && ([extension caseInsensitiveCompare:@"webp"] == NSOrderedSame)) {
//看看是否已经处理过了，防止无限循环
if ([NSURLProtocol propertyForKey:URLProtocolHandledKey inRequest:request]) {
return NO;
}
return YES;
}
return NO;
}
+ (NSURLRequest *) canonicalRequestForRequest:(NSURLRequest *)request {
return request;
}
#pragma mark 通信协议内容实现
- (void)startLoading
{
NSMutableURLRequest *mutableReqeust = [[self request] mutableCopy];
//标示改request已经处理过了，防止无限循环
[NSURLProtocol setProperty:@YES forKey:URLProtocolHandledKey inRequest:mutableReqeust];
NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
self.session = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:[NSOperationQueue currentQueue]];
//判断是否缓存
NSString *name = [NSString stringWithFormat:@"%@.jpg", self.request.URL.absoluteString];
NSString *path = [NSTemporaryDirectory() stringByAppendingPathComponent:name];
if([[NSFileManager defaultManager] fileExistsAtPath:path]) {
mutableReqeust.URL = [NSURL fileURLWithPath:path];
}
[[self.session dataTaskWithRequest:mutableReqeust] resume];
}
- (void)stopLoading
{
[self.session invalidateAndCancel];
}
#pragma mark dataDelegate
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler
{
[self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
if (completionHandler) {
completionHandler(NSURLSessionResponseAllow);
}
}
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data{
NSData *transData = data;
NSString *extension = [dataTask.currentRequest.URL pathExtension];
if ([extension caseInsensitiveCompare:@"webp"] == NSOrderedSame) {
UIImage *imgData = [UIImage sd_imageWithWebPData:data];
transData = UIImageJPEGRepresentation(imgData, 1.0f);
//写入缓存
NSString *name = [NSString stringWithFormat:@"%@.jpg", dataTask.currentRequest.URL.absoluteString];
NSString *path = [NSTemporaryDirectory() stringByAppendingPathComponent:name];
if (transData != nil) {
BOOL yy = [transData writeToFile:path atomically:YES];
if (yy) {
NSLog(@"写入成功");
}
}
}
[self.client URLProtocol:self didLoadData:transData];
}
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(nullable NSError *)error{
if (error) {
[self.client URLProtocol:self didFailWithError:error];
}else{
[self.client URLProtocolDidFinishLoading:self];
}
}
@end
记得再delegate里注册该协议：
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
//注册protocol
[NSURLProtocol registerClass:[CYCustomURLProtocal class]];
return YES;
}
有两个注意点:
-
NSURLProtocol会影响 App 内所有请求,稍有遗漏的话后果比较严重,要慎重,所以最好是限定只有webp格式的图片才走这个自定义协议。 - 不论 NSURLConnection 还是 NSURLSession,尽量把
URLProtocol didFailWithError,URLProtocol DidFinishLoading,URLProtocol didLoadData,URLProtocol didReceiveResponse几个方法写全,避免网络请求产生不可预知的 BUG
4.最后
仅以此记录一下调研结果。
demo附上：https://github.com/sharon5mayday5/iOS_WebP.git
