改进wl。的答案,这是一种基于签名来预测图像的MIME类型的更扩展,更精确的方法。该代码主要受php的ext / standard / image.c启发。
- (NSString *)mimeTypeByGuessingFromData:(NSData *)data {
char bytes[12] = {0};
[data getBytes:&bytes length:12];
const char bmp[2] = {'B', 'M'};
const char gif[3] = {'G', 'I', 'F'};
const char swf[3] = {'F', 'W', 'S'};
const char swc[3] = {'C', 'W', 'S'};
const char jpg[3] = {0xff, 0xd8, 0xff};
const char psd[4] = {'8', 'B', 'P', 'S'};
const char iff[4] = {'F', 'O', 'R', 'M'};
const char webp[4] = {'R', 'I', 'F', 'F'};
const char ico[4] = {0x00, 0x00, 0x01, 0x00};
const char tif_ii[4] = {'I','I', 0x2A, 0x00};
const char tif_mm[4] = {'M','M', 0x00, 0x2A};
const char png[8] = {0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a};
const char jp2[12] = {0x00, 0x00, 0x00, 0x0c, 0x6a, 0x50, 0x20, 0x20, 0x0d, 0x0a, 0x87, 0x0a};
if (!memcmp(bytes, bmp, 2)) {
return @"image/x-ms-bmp";
} else if (!memcmp(bytes, gif, 3)) {
return @"image/gif";
} else if (!memcmp(bytes, jpg, 3)) {
return @"image/jpeg";
} else if (!memcmp(bytes, psd, 4)) {
return @"image/psd";
} else if (!memcmp(bytes, iff, 4)) {
return @"image/iff";
} else if (!memcmp(bytes, webp, 4)) {
return @"image/webp";
} else if (!memcmp(bytes, ico, 4)) {
return @"image/vnd.microsoft.icon";
} else if (!memcmp(bytes, tif_ii, 4) || !memcmp(bytes, tif_mm, 4)) {
return @"image/tiff";
} else if (!memcmp(bytes, png, 8)) {
return @"image/png";
} else if (!memcmp(bytes, jp2, 12)) {
return @"image/jp2";
}
return @"application/octet-stream";
}
上面的方法可以识别以下图像类型:
image/x-ms-bmp
(bmp)
image/gif
(gif)
image/jpeg
(jpg,jpeg)
image/psd
(psd)
image/iff
(iff)
image/webp
(webp)
image/vnd.microsoft.icon
(ico)
image/tiff
(tif,tiff)
image/png
(png)
image/jp2
(jp2)
不幸的是,没有简单的方法可以从UIImage
实例中获取此类信息,因为无法访问其封装的位图数据。