86 lines
1.8 KiB
Go
86 lines
1.8 KiB
Go
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package pngstructure
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import (
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"bufio"
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"bytes"
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"image"
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"io"
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"os"
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"image/png"
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riimage "github.com/dsoprea/go-utility/v2/image"
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)
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// PngMediaParser knows how to parse a PNG stream.
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type PngMediaParser struct {
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}
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// NewPngMediaParser returns a new `PngMediaParser`.
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func NewPngMediaParser() riimage.MediaParser {
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return new(PngMediaParser)
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}
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// Parse parses a PNG stream given a `io.ReadSeeker`.
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func (pmp *PngMediaParser) Parse(
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rs io.ReadSeeker,
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size int,
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) (riimage.MediaContext, error) {
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ps := NewPngSplitter()
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if err := ps.readHeader(rs); err != nil {
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return nil, err
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}
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s := bufio.NewScanner(rs)
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// Since each segment can be any
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// size, our buffer must be allowed
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// to grow as large as the file.
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buffer := []byte{}
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s.Buffer(buffer, size)
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s.Split(ps.Split)
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for s.Scan() {
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}
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if err := s.Err(); err != nil {
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return nil, err
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}
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return ps.Chunks()
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}
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// ParseFile parses a PNG stream given a file-path.
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func (pmp *PngMediaParser) ParseFile(filepath string) (riimage.MediaContext, error) {
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f, err := os.Open(filepath)
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if err != nil {
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return nil, err
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}
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defer f.Close()
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stat, err := f.Stat()
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if err != nil {
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return nil, err
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}
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size := stat.Size()
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return pmp.Parse(f, int(size))
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}
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// ParseBytes parses a PNG stream given a byte-slice.
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func (pmp *PngMediaParser) ParseBytes(data []byte) (riimage.MediaContext, error) {
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br := bytes.NewReader(data)
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return pmp.Parse(br, len(data))
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}
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// LooksLikeFormat returns a boolean indicating
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// whether the stream looks like a PNG image.
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func (pmp *PngMediaParser) LooksLikeFormat(data []byte) bool {
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return bytes.Equal(data[:len(PngSignature)], PngSignature[:])
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}
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// GetImage returns an image.Image-compatible struct.
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func (pmp *PngMediaParser) GetImage(r io.Reader) (img image.Image, err error) {
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return png.Decode(r)
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}
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