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