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/*
GoToSocial
Copyright (C) 2021-2023 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"
"io"
"github.com/buckket/go-blurhash"
"github.com/disintegration/imaging"
_ "golang.org/x/image/webp" // blank import to support WebP decoding
)
const (
thumbnailMaxWidth = 512
thumbnailMaxHeight = 512
)
func decodeGif(r io.Reader) (*mediaMeta, error) {
gif, err := gif.DecodeAll(r)
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 := float32(width) / float32(height)
return &mediaMeta{
width: width,
height: height,
size: size,
aspect: aspect,
}, nil
}
func decodeImage(r io.Reader, contentType string) (*mediaMeta, error) {
var i image.Image
var err error
switch contentType {
case mimeImageJpeg, mimeImageWebp:
i, err = imaging.Decode(r, imaging.AutoOrientation(true))
case mimeImagePng:
strippedPngReader := io.Reader(&PNGAncillaryChunkStripper{
Reader: r,
})
i, err = imaging.Decode(strippedPngReader, imaging.AutoOrientation(true))
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 := float32(width) / float32(height)
return &mediaMeta{
width: width,
height: height,
size: size,
aspect: aspect,
}, nil
}
// deriveStaticEmojji takes a given gif or png of an emoji, decodes it, and re-encodes it as a static png.
func deriveStaticEmoji(r io.Reader, contentType string) (*mediaMeta, error) {
var i image.Image
var err error
switch contentType {
case mimeImagePng:
i, err = StrippedPngDecode(r)
if err != nil {
return nil, err
}
case mimeImageGif:
i, err = gif.Decode(r)
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 &mediaMeta{
small: out.Bytes(),
}, nil
}
// deriveThumbnailFromImage returns a byte slice and metadata for a thumbnail
// of a given piece of media, 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 deriveThumbnailFromImage(r io.Reader, contentType string, createBlurhash bool) (*mediaMeta, error) {
var i image.Image
var err error
switch contentType {
case mimeImageJpeg, mimeImageGif, mimeImageWebp:
i, err = imaging.Decode(r, imaging.AutoOrientation(true))
case mimeImagePng:
strippedPngReader := io.Reader(&PNGAncillaryChunkStripper{
Reader: r,
})
i, err = imaging.Decode(strippedPngReader, imaging.AutoOrientation(true))
default:
err = fmt.Errorf("content type %s can't be thumbnailed as an image", contentType)
}
if err != nil {
return nil, fmt.Errorf("error decoding %s: %s", contentType, err)
}
originalX := i.Bounds().Size().X
originalY := i.Bounds().Size().Y
var thumb image.Image
if originalX <= thumbnailMaxWidth && originalY <= thumbnailMaxHeight {
// it's already small, no need to resize
thumb = i
} else {
thumb = imaging.Fit(i, thumbnailMaxWidth, thumbnailMaxHeight, imaging.Linear)
}
thumbX := thumb.Bounds().Size().X
thumbY := thumb.Bounds().Size().Y
size := thumbX * thumbY
aspect := float32(thumbX) / float32(thumbY)
im := &mediaMeta{
width: thumbX,
height: thumbY,
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 := imaging.Resize(thumb, 32, 0, imaging.NearestNeighbor)
bh, err := blurhash.Encode(4, 3, tiny)
if err != nil {
return nil, fmt.Errorf("error creating blurhash: %s", 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, fmt.Errorf("error encoding thumbnail: %s", err)
}
im.small = out.Bytes()
return im, nil
}
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