根据图片url获取图片尺寸
// 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;
}
}
}
原文链接：https://www.oschina.net/code/snippet_2248391_53038