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package kitty
import (
"compress/zlib"
"fmt"
"image"
"image/color"
"image/png"
"io"
)
// Decoder is a decoder for the Kitty graphics protocol. It supports decoding
// images in the 24-bit [RGB], 32-bit [RGBA], and [PNG] formats. It can also
// decompress data using zlib.
// The default format is 32-bit [RGBA].
type Decoder struct {
// Uses zlib decompression.
Decompress bool
// Can be one of [RGB], [RGBA], or [PNG].
Format int
// Width of the image in pixels. This can be omitted if the image is [PNG]
// formatted.
Width int
// Height of the image in pixels. This can be omitted if the image is [PNG]
// formatted.
Height int
}
// Decode decodes the image data from r in the specified format.
func (d *Decoder) Decode(r io.Reader) (image.Image, error) {
if d.Decompress {
zr, err := zlib.NewReader(r)
if err != nil {
return nil, fmt.Errorf("failed to create zlib reader: %w", err)
}
defer zr.Close() //nolint:errcheck
r = zr
}
if d.Format == 0 {
d.Format = RGBA
}
switch d.Format {
case RGBA, RGB:
return d.decodeRGBA(r, d.Format == RGBA)
case PNG:
return png.Decode(r)
default:
return nil, fmt.Errorf("unsupported format: %d", d.Format)
}
}
// decodeRGBA decodes the image data in 32-bit RGBA or 24-bit RGB formats.
func (d *Decoder) decodeRGBA(r io.Reader, alpha bool) (image.Image, error) {
m := image.NewRGBA(image.Rect(0, 0, d.Width, d.Height))
var buf []byte
if alpha {
buf = make([]byte, 4)
} else {
buf = make([]byte, 3)
}
for y := 0; y < d.Height; y++ {
for x := 0; x < d.Width; x++ {
if _, err := io.ReadFull(r, buf[:]); err != nil {
return nil, fmt.Errorf("failed to read pixel data: %w", err)
}
if alpha {
m.SetRGBA(x, y, color.RGBA{buf[0], buf[1], buf[2], buf[3]})
} else {
m.SetRGBA(x, y, color.RGBA{buf[0], buf[1], buf[2], 0xff})
}
}
}
return m, nil
}
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