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/*
GoToSocial
Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
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"
)
const (
thumbnailMaxWidth = 512
thumbnailMaxHeight = 512
)
type ImageMeta struct {
image []byte
width int
height int
size int
aspect float64
blurhash string
}
func decodeGif(b []byte) (*ImageMeta, error) {
gif, err := gif.DecodeAll(bytes.NewReader(b))
if err != nil {
return nil, err
}
// use the first frame to get the static characteristics
width := gif.Config.Width
height := gif.Config.Height
size := width * height
aspect := float64(width) / float64(height)
return &ImageMeta{
image: b,
width: width,
height: height,
size: size,
aspect: aspect,
}, nil
}
func decodeImage(b []byte, contentType string) (*ImageMeta, error) {
var i image.Image
var err error
switch contentType {
case mimeImageJpeg:
i, err = jpeg.Decode(bytes.NewReader(b))
case mimeImagePng:
i, err = png.Decode(bytes.NewReader(b))
default:
err = fmt.Errorf("content type %s not recognised", contentType)
}
if err != nil {
return nil, err
}
if i == nil {
return nil, errors.New("processed image was nil")
}
width := i.Bounds().Size().X
height := i.Bounds().Size().Y
size := width * height
aspect := float64(width) / float64(height)
return &ImageMeta{
image: b,
width: width,
height: height,
size: size,
aspect: aspect,
}, nil
}
// deriveThumbnail returns a byte slice and metadata for a thumbnail
// of a given jpeg, png, or gif, or an error if something goes wrong.
//
// If createBlurhash is true, then a blurhash will also be generated from a tiny
// version of the image. This costs precious CPU cycles, so only use it if you
// really need a blurhash and don't have one already.
//
// If createBlurhash is false, then the blurhash field on the returned ImageAndMeta
// will be an empty string.
func deriveThumbnail(b []byte, contentType string, createBlurhash bool) (*ImageMeta, error) {
var i image.Image
var err error
switch contentType {
case mimeImageJpeg:
i, err = jpeg.Decode(bytes.NewReader(b))
case mimeImagePng:
i, err = png.Decode(bytes.NewReader(b))
case mimeImageGif:
i, err = gif.Decode(bytes.NewReader(b))
default:
err = fmt.Errorf("content type %s can't be thumbnailed", contentType)
}
if err != nil {
return nil, err
}
if i == nil {
return nil, errors.New("processed image was nil")
}
thumb := resize.Thumbnail(thumbnailMaxWidth, thumbnailMaxHeight, i, resize.NearestNeighbor)
width := thumb.Bounds().Size().X
height := thumb.Bounds().Size().Y
size := width * height
aspect := float64(width) / float64(height)
im := &ImageMeta{
width: width,
height: height,
size: size,
aspect: aspect,
}
if createBlurhash {
// for generating blurhashes, it's more cost effective to lose detail rather than
// pass a big image into the blurhash algorithm, so make a teeny tiny version
tiny := resize.Thumbnail(32, 32, thumb, resize.NearestNeighbor)
bh, err := blurhash.Encode(4, 3, tiny)
if err != nil {
return nil, err
}
im.blurhash = bh
}
out := &bytes.Buffer{}
if err := jpeg.Encode(out, thumb, &jpeg.Options{
// Quality isn't extremely important for thumbnails, so 75 is "good enough"
Quality: 75,
}); err != nil {
return nil, err
}
im.image = out.Bytes()
return im, 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) (*ImageMeta, 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 &ImageMeta{
image: out.Bytes(),
}, nil
}
// 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
}
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