1 files changed, 140 insertions, 0 deletions
diff --git a/internal/media/video.go b/internal/media/video.go
new file mode 100644
index 000000000..ef486d63d
--- /dev/null
+++ b/internal/media/video.go
@@ -0,0 +1,140 @@
+/*
+   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/color"
+	"image/draw"
+	"image/jpeg"
+	"io"
+	"os"
+
+	"github.com/abema/go-mp4"
+	"github.com/superseriousbusiness/gotosocial/internal/log"
+)
+
+var thumbFill = color.RGBA{42, 43, 47, 0} // the color to fill video thumbnails with
+
+func decodeVideo(r io.Reader, contentType string) (*mediaMeta, error) {
+	// We'll need a readseeker to decode the video. We can get a readseeker
+	// without burning too much mem by first copying the reader into a temp file.
+	// First create the file in the temporary directory...
+	tempFile, err := os.CreateTemp(os.TempDir(), "gotosocial-")
+	if err != nil {
+		return nil, fmt.Errorf("could not create temporary file while decoding video: %w", err)
+	}
+	tempFileName := tempFile.Name()
+
+	// Make sure to clean up the temporary file when we're done with it
+	defer func() {
+		if err := tempFile.Close(); err != nil {
+			log.Errorf("could not close file %s: %s", tempFileName, err)
+		}
+		if err := os.Remove(tempFileName); err != nil {
+			log.Errorf("could not remove file %s: %s", tempFileName, err)
+		}
+	}()
+
+	// Now copy the entire reader we've been provided into the
+	// temporary file; we won't use the reader again after this.
+	if _, err := io.Copy(tempFile, r); err != nil {
+		return nil, fmt.Errorf("could not copy video reader into temporary file %s: %w", tempFileName, err)
+	}
+
+	// define some vars we need to pull the width/height out of the video
+	var (
+		height      int
+		width       int
+		readHandler = getReadHandler(&height, &width)
+	)
+
+	// do the actual decoding here, providing the temporary file we created as readseeker
+	if _, err := mp4.ReadBoxStructure(tempFile, readHandler); err != nil {
+		return nil, fmt.Errorf("parsing video data: %w", err)
+	}
+
+	// width + height should now be updated by the readHandler
+	return &mediaMeta{
+		width:  width,
+		height: height,
+		size:   height * width,
+		aspect: float64(width) / float64(height),
+	}, nil
+}
+
+// getReadHandler returns a handler function that updates the underling
+// values of the given height and width int pointers to the hightest and
+// widest points of the video.
+func getReadHandler(height *int, width *int) func(h *mp4.ReadHandle) (interface{}, error) {
+	return func(rh *mp4.ReadHandle) (interface{}, error) {
+		if rh.BoxInfo.Type == mp4.BoxTypeTkhd() {
+			box, _, err := rh.ReadPayload()
+			if err != nil {
+				return nil, fmt.Errorf("could not read mp4 payload: %w", err)
+			}
+
+			tkhd, ok := box.(*mp4.Tkhd)
+			if !ok {
+				return nil, errors.New("box was not of type *mp4.Tkhd")
+			}
+
+			// if height + width of this box are greater than what
+			// we have stored, then update our stored values
+			if h := int(tkhd.GetHeight()); h > *height {
+				*height = h
+			}
+
+			if w := int(tkhd.GetWidth()); w > *width {
+				*width = w
+			}
+		}
+
+		if rh.BoxInfo.IsSupportedType() {
+			return rh.Expand()
+		}
+
+		return nil, nil
+	}
+}
+
+func deriveThumbnailFromVideo(height int, width int) (*mediaMeta, error) {
+	// create a rectangle with the same dimensions as the video
+	img := image.NewRGBA(image.Rect(0, 0, width, height))
+
+	// fill the rectangle with our desired fill color
+	draw.Draw(img, img.Bounds(), &image.Uniform{thumbFill}, image.Point{}, draw.Src)
+
+	// we can get away with using extremely poor quality for this monocolor thumbnail
+	out := &bytes.Buffer{}
+	if err := jpeg.Encode(out, img, &jpeg.Options{Quality: 1}); err != nil {
+		return nil, fmt.Errorf("error encoding video thumbnail: %w", err)
+	}
+
+	return &mediaMeta{
+		width:  width,
+		height: height,
+		size:   width * height,
+		aspect: float64(width) / float64(height),
+		small:  out.Bytes(),
+	}, nil
+}