cli/internal/sniff/image.go

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2022-11-21 22:45:18 +00:00
package sniff
// ref: https://mimesniff.spec.whatwg.org
var imageMIMEs = map[string]Sniffer{
"image/jpeg": prefixSniffer{0xFF, 0xD8, 0xFF},
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"image/png": prefixSniffer{0x89, 'P', 'N', 'G', '\r', '\n', 0x1A, '\n'},
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"image/bmp": prefixSniffer("BM"),
"image/webp": prefixSniffer("RIFF"),
"image/gif": prefixSniffer("GIF8"),
}
// ImageMIME sniffs the well-known image types, and returns its MIME.
func ImageMIME(header []byte) (string, bool) {
for ext, sniffer := range imageMIMEs {
if sniffer.Sniff(header) {
return ext, true
}
}
return "", false
}
// ImageExtension is equivalent to ImageMIME, but returns file extension
func ImageExtension(header []byte) (string, bool) {
ext, ok := ImageMIME(header)
if !ok {
return "", false
}
// todo: use mime.ExtensionsByType
return "." + ext[6:], true // "image/" is 6 bytes
}