ImageSizeExplorer.m

//
//  ImageSizeExplorer.m
//  WKMoments
//
//  Created by Jack on 16/1/21.
//  Copyright © 2016年 WenKang. All rights reserved.
//

#import "ImageSizeExplorer.h"

@implementation ImageSizeExplorer

+ (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;
    
    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)) {
        NSData* data = [NSURLConnection sendSynchronousRequest:[NSURLRequest requestWithURL:URL] returningResponse:nil error:nil];
        UIImage* image = [UIImage imageWithData:data];
        if (image) {
            size = image.size;
        }
    }
    return size;
}

+ (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;
}

+ (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;
}

+ (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;
        }
    }
}

@end