iOS根据图片url获取尺寸

可以在uiimage的分类中加入下面的代码,并且引入系统的imageio.framework

/**
 根据图片的url获取尺寸

 @param url url
 @return cgsize
 */
+ (cgsize)getimagesizewithurl:(id)url;

/**
 *  根据图片url获取图片尺寸
 */
+ (cgsize)getimagesizewithurl:(id)url{
    nsurl * url = nil;
    if ([url iskindofclass:[nsurl class]]) {
        url = url;
    }
    if ([url iskindofclass:[nsstring class]]) {
        url = [nsurl urlwithstring:url];
    }
    if (!url) {
        return cgsizezero;
    }
    cgimagesourceref imagesourceref =     cgimagesourcecreatewithurl((cfurlref)url, null);
    cgfloat width = 0, height = 0;
    if (imagesourceref) {
        cfdictionaryref imageproperties = cgimagesourcecopypropertiesatindex(imagesourceref, 0, null);
        if (imageproperties != null) {
            cfnumberref widthnumberref = cfdictionarygetvalue(imageproperties, kcgimagepropertypixelwidth);
            if (widthnumberref != null) {
                cfnumbergetvalue(widthnumberref, kcfnumberfloat64type, &width);
            }
            cfnumberref heightnumberref = cfdictionarygetvalue(imageproperties, kcgimagepropertypixelheight);
            if (heightnumberref != null) {
                cfnumbergetvalue(heightnumberref, kcfnumberfloat64type, &height);
            }
            cfrelease(imageproperties);
        }
        cfrelease(imagesourceref);
    }
    return cgsizemake(width, height);
}

实践证明,网上的另外一种方法是不可行存在问题的,贴上所示的图片url:http://xs3.op.xywy.com/club.xywy.com/doc/20181017/0fd2a51f9435a4.jpg

// 根据图片url获取图片尺寸
-(cgsize)getimagesizewithurl:(id)imageurl
{
    nsurl* url = nil;
    if([imageurl iskindofclass:[nsurl class]]){
        url = imageurl;
    }
    if([imageurl iskindofclass:[nsstring class]]){
        url = [nsurl urlwithstring:imageurl];
    }
    if(url == nil)
        return cgsizezero;                  // url不正确返回cgsizezero
    
    nsmutableurlrequest *request = [[nsmutableurlrequest alloc] initwithurl:url];
    nsstring* pathextendsion = [url.pathextension lowercasestring];
    
    cgsize size = cgsizezero;
    if([pathextendsion isequaltostring:@"png"]){
        size =  [self getpngimagesizewithrequest:request];
    }
    else if([pathextendsion isequal:@"gif"])
    {
        size =  [self getgifimagesizewithrequest:request];
    }
    else{
        size = [self getjpgimagesizewithrequest:request];
    }
    if(cgsizeequaltosize(cgsizezero, size))                    // 如果获取文件头信息失败,发送异步请求请求原图
    {
        nsdata* data = [nsurlconnection sendsynchronousrequest:[nsurlrequest requestwithurl:url] returningresponse:nil error:nil];
        uiimage* image = [uiimage imagewithdata:data];
        if(image)
        {
            size = image.size;
        }
    }
    return size;
}
//  获取png图片的大小
-(cgsize)getpngimagesizewithrequest:(nsmutableurlrequest*)request
{
    [request setvalue:@"bytes=16-23" forhttpheaderfield:@"range"];
    nsdata* data = [nsurlconnection sendsynchronousrequest:request returningresponse:nil error:nil];
    if(data.length == 8)
    {
        int w1 = 0, w2 = 0, w3 = 0, w4 = 0;
        [data getbytes:&w1 range:nsmakerange(0, 1)];
        [data getbytes:&w2 range:nsmakerange(1, 1)];
        [data getbytes:&w3 range:nsmakerange(2, 1)];
        [data getbytes:&w4 range:nsmakerange(3, 1)];
        int w = (w1 << 24) + (w2 << 16) + (w3 << 8) + w4;
        int h1 = 0, h2 = 0, h3 = 0, h4 = 0;
        [data getbytes:&h1 range:nsmakerange(4, 1)];
        [data getbytes:&h2 range:nsmakerange(5, 1)];
        [data getbytes:&h3 range:nsmakerange(6, 1)];
        [data getbytes:&h4 range:nsmakerange(7, 1)];
        int h = (h1 << 24) + (h2 << 16) + (h3 << 8) + h4;
        return cgsizemake(w, h);
    }
    return cgsizezero;
}
//  获取gif图片的大小
-(cgsize)getgifimagesizewithrequest:(nsmutableurlrequest*)request
{
    [request setvalue:@"bytes=6-9" forhttpheaderfield:@"range"];
    nsdata* data = [nsurlconnection sendsynchronousrequest:request returningresponse:nil error:nil];
    if(data.length == 4)
    {
        short w1 = 0, w2 = 0;
        [data getbytes:&w1 range:nsmakerange(0, 1)];
        [data getbytes:&w2 range:nsmakerange(1, 1)];
        short w = w1 + (w2 << 8);
        short h1 = 0, h2 = 0;
        [data getbytes:&h1 range:nsmakerange(2, 1)];
        [data getbytes:&h2 range:nsmakerange(3, 1)];
        short h = h1 + (h2 << 8);
        return cgsizemake(w, h);
    }
    return cgsizezero;
}
//  获取jpg图片的大小
-(cgsize)getjpgimagesizewithrequest:(nsmutableurlrequest*)request
{
    [request setvalue:@"bytes=0-209" forhttpheaderfield:@"range"];
    nsdata* data = [nsurlconnection sendsynchronousrequest:request returningresponse:nil error:nil];
    
    if ([data length] <= 0x58) {
        return cgsizezero;
    }
    
    if ([data length] < 210) {// 肯定只有一个dqt字段
        short w1 = 0, w2 = 0;
        [data getbytes:&w1 range:nsmakerange(0x60, 0x1)];
        [data getbytes:&w2 range:nsmakerange(0x61, 0x1)];
        short w = (w1 << 8) + w2;
        short h1 = 0, h2 = 0;
        [data getbytes:&h1 range:nsmakerange(0x5e, 0x1)];
        [data getbytes:&h2 range:nsmakerange(0x5f, 0x1)];
        short h = (h1 << 8) + h2;
        return cgsizemake(w, h);
    } else {
        short word = 0x0;
        [data getbytes:&word range:nsmakerange(0x15, 0x1)];
        if (word == 0xdb) {
            [data getbytes:&word range:nsmakerange(0x5a, 0x1)];
            if (word == 0xdb) {// 两个dqt字段
                short w1 = 0, w2 = 0;
                [data getbytes:&w1 range:nsmakerange(0xa5, 0x1)];
                [data getbytes:&w2 range:nsmakerange(0xa6, 0x1)];
                short w = (w1 << 8) + w2;
                short h1 = 0, h2 = 0;
                [data getbytes:&h1 range:nsmakerange(0xa3, 0x1)];
                [data getbytes:&h2 range:nsmakerange(0xa4, 0x1)];
                short h = (h1 << 8) + h2;
                return cgsizemake(w, h);
            } else {// 一个dqt字段
                short w1 = 0, w2 = 0;
                [data getbytes:&w1 range:nsmakerange(0x60, 0x1)];
                [data getbytes:&w2 range:nsmakerange(0x61, 0x1)];
                short w = (w1 << 8) + w2;
                short h1 = 0, h2 = 0;
                [data getbytes:&h1 range:nsmakerange(0x5e, 0x1)];
                [data getbytes:&h2 range:nsmakerange(0x5f, 0x1)];
                short h = (h1 << 8) + h2;
                return cgsizemake(w, h);
            }
        } else {
            return cgsizezero;
        }
    }
}

源自:https://www.jianshu.com/p/9984c37f3f54