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49 lines
926 B
Go
49 lines
926 B
Go
package imagesize
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import (
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"bytes"
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"encoding/binary"
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"io"
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)
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var bmpMagick = []byte("BM")
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type BmpFormatError string
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func (e BmpFormatError) Error() string { return "invalid BMP format: " + string(e) }
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func DecodeBmpMeta(r io.Reader) (*Meta, error) {
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var tmp [26]byte
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if _, err := io.ReadFull(r, tmp[:]); err != nil {
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return nil, err
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}
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if !bytes.Equal(tmp[:2], bmpMagick) {
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return nil, BmpFormatError("malformed header")
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}
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infoSize := binary.LittleEndian.Uint32(tmp[14:18])
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var width, height int
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if infoSize >= 40 {
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width = int(binary.LittleEndian.Uint32(tmp[18:22]))
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height = int(binary.LittleEndian.Uint32(tmp[22:26]))
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} else {
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// CORE
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width = int(binary.LittleEndian.Uint16(tmp[18:20]))
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height = int(binary.LittleEndian.Uint16(tmp[20:22]))
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}
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return &Meta{
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Format: "bmp",
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Width: width,
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Height: height,
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}, nil
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}
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func init() {
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RegisterFormat(string(bmpMagick), DecodeBmpMeta)
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}
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