Add in-memory screenshot generation for sprites and phash (#1316)

pkg/ffmpeg/encoder_sprite_screenshot.go

@@ -0,0 +1,38 @@
+package ffmpeg
+
+import (
+	"fmt"
+	"image"
+	"strings"
+)
+
+type SpriteScreenshotOptions struct {
+	Time  float64
+	Width int
+}
+
+func (e *Encoder) SpriteScreenshot(probeResult VideoFile, options SpriteScreenshotOptions) (image.Image, error) {
+	args := []string{
+		"-v", "error",
+		"-ss", fmt.Sprintf("%v", options.Time),
+		"-i", probeResult.Path,
+		"-vframes", "1",
+		"-vf", fmt.Sprintf("scale=%v:-1", options.Width),
+		"-c:v", "bmp",
+		"-f", "rawvideo",
+		"-",
+	}
+	data, err := e.run(probeResult, args)
+	if err != nil {
+		return nil, err
+	}
+
+	reader := strings.NewReader(data)
+
+	img, _, err := image.Decode(reader)
+	if err != nil {
+		return nil, err
+	}
+
+	return img, err
+}