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/*
* Copyright (C) 2016 ~ 2018 Deepin Technology Co., Ltd.
*
* Author: jouyouyun <jouyouwen717@gmail.com>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package graphic
import (
"bufio"
"os"
)
type format struct {
name, magic string
}
// image formats:
var formats = []format{
{"jpeg", "\xff\xd8"},
{"bmp", "BM????\x00\x00\x00\x00"},
{"png", "\x89PNG\r\n\x1a\n"},
{"tiff", "MM\x00\x2A"}, // little-endian
{"tiff", "II\x2A\x00"}, // big-endian
{"gif", "GIF8?a"},
}
// Sniff determines the format of r's data.
func sniff(r *bufio.Reader) format {
for _, f := range formats {
b, err := r.Peek(len(f.magic))
if err == nil && match(f.magic, b) {
return f
}
}
return format{}
}
// Match reports whether magic matches b. Magic may contain "?" wildcards.
func match(magic string, b []byte) bool {
if len(magic) != len(b) {
return false
}
for i, c := range b {
if magic[i] != c && magic[i] != '?' {
return false
}
}
return true
}
func SniffImageFormat(file string) (string, error) {
fh, err := os.Open(file)
if err != nil {
return "", err
}
defer fh.Close()
reader := bufio.NewReader(fh)
format := sniff(reader)
return format.name, nil
}
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