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package media
import (
"bytes"
"errors"
"fmt"
"image"
"image/gif"
"image/jpeg"
"image/png"
"github.com/buckket/go-blurhash"
"github.com/nfnt/resize"
"github.com/superseriousbusiness/exifremove/pkg/exifremove"
)
// purgeExif is a little wrapper for the action of removing exif data from an image.
// Only pass pngs or jpegs to this function.
func purgeExif(data []byte) ([]byte, error) {
if len(data) == 0 {
return nil, errors.New("passed image was not valid")
}
clean, err := exifremove.Remove(data)
if err != nil {
return nil, fmt.Errorf("could not purge exif from image: %s", err)
}
if len(clean) == 0 {
return nil, errors.New("purged image was not valid")
}
return clean, nil
}
func deriveGif(b []byte, extension string) (*imageAndMeta, error) {
var g *gif.GIF
var err error
switch extension {
case mimeGif:
g, err = gif.DecodeAll(bytes.NewReader(b))
if err != nil {
return nil, err
}
default:
return nil, fmt.Errorf("extension %s not recognised", extension)
}
// use the first frame to get the static characteristics
width := g.Config.Width
height := g.Config.Height
size := width * height
aspect := float64(width) / float64(height)
return &imageAndMeta{
image: b,
width: width,
height: height,
size: size,
aspect: aspect,
}, nil
}
func deriveImage(b []byte, contentType string) (*imageAndMeta, error) {
var i image.Image
var err error
switch contentType {
case mimeImageJpeg:
i, err = jpeg.Decode(bytes.NewReader(b))
if err != nil {
return nil, err
}
case mimeImagePng:
i, err = png.Decode(bytes.NewReader(b))
if err != nil {
return nil, err
}
default:
return nil, fmt.Errorf("content type %s not recognised", contentType)
}
width := i.Bounds().Size().X
height := i.Bounds().Size().Y
size := width * height
aspect := float64(width) / float64(height)
return &imageAndMeta{
image: b,
width: width,
height: height,
size: size,
aspect: aspect,
}, nil
}
// deriveThumbnail returns a byte slice and metadata for a thumbnail of width x and height y,
// of a given jpeg, png, or gif, or an error if something goes wrong.
//
// Note that the aspect ratio of the image will be retained,
// so it will not necessarily be a square, even if x and y are set as the same value.
func deriveThumbnail(b []byte, contentType string, x uint, y uint) (*imageAndMeta, error) {
var i image.Image
var err error
switch contentType {
case mimeImageJpeg:
i, err = jpeg.Decode(bytes.NewReader(b))
if err != nil {
return nil, err
}
case mimeImagePng:
i, err = png.Decode(bytes.NewReader(b))
if err != nil {
return nil, err
}
case mimeImageGif:
i, err = gif.Decode(bytes.NewReader(b))
if err != nil {
return nil, err
}
default:
return nil, fmt.Errorf("content type %s not recognised", contentType)
}
thumb := resize.Thumbnail(x, y, i, resize.NearestNeighbor)
width := thumb.Bounds().Size().X
height := thumb.Bounds().Size().Y
size := width * height
aspect := float64(width) / float64(height)
tiny := resize.Thumbnail(32, 32, thumb, resize.NearestNeighbor)
bh, err := blurhash.Encode(4, 3, tiny)
if err != nil {
return nil, err
}
out := &bytes.Buffer{}
if err := jpeg.Encode(out, thumb, &jpeg.Options{
Quality: 75,
}); err != nil {
return nil, err
}
return &imageAndMeta{
image: out.Bytes(),
width: width,
height: height,
size: size,
aspect: aspect,
blurhash: bh,
}, nil
}
// deriveStaticEmojji takes a given gif or png of an emoji, decodes it, and re-encodes it as a static png.
func deriveStaticEmoji(b []byte, contentType string) (*imageAndMeta, error) {
var i image.Image
var err error
switch contentType {
case mimeImagePng:
i, err = png.Decode(bytes.NewReader(b))
if err != nil {
return nil, err
}
case mimeImageGif:
i, err = gif.Decode(bytes.NewReader(b))
if err != nil {
return nil, err
}
default:
return nil, fmt.Errorf("content type %s not allowed for emoji", contentType)
}
out := &bytes.Buffer{}
if err := png.Encode(out, i); err != nil {
return nil, err
}
return &imageAndMeta{
image: out.Bytes(),
}, nil
}
type imageAndMeta struct {
image []byte
width int
height int
size int
aspect float64
blurhash string
}
|
