Scanner: Remove black bars on thumbnails (#810)

* Scanner: Crop black bars on thumbnails

* Docker: Scanner: Move to alpine to get a newer ffmpeg version

scanner/Dockerfile

@@ -1,6 +1,5 @@
-FROM golang:1.22.6-bullseye AS builder
+FROM golang:1.22.6-alpine AS builder
 RUN go install github.com/swaggo/swag/cmd/swag@latest
-RUN apt-get update -y; apt-get install -y ffmpeg
 WORKDIR /app
 COPY go.mod go.sum ./
 RUN go mod download
@@ -9,12 +8,12 @@ COPY ./internal ./internal
 RUN swag init -d app -o ./app/docs
 RUN GOOS=linux go build -o ./scanner ./app
 
-FROM debian:bullseye-slim AS runner
+FROM golang:1.22.6-alpine AS runner
 
 ENV SERVICE_NAME="scanner"
-RUN useradd -ms /bin/false $SERVICE_NAME
+RUN adduser --disabled-password -s /bin/false $SERVICE_NAME
 
-RUN apt-get update -y; apt-get install -y ffmpeg wget libchromaprint-tools libchromaprint-dev libfftw3-dev
+RUN apk update && apk upgrade && apk add ffmpeg chromaprint mailcap 
 WORKDIR /app
 COPY --from=builder /app/scanner ./
 USER $SERVICE_NAME

scanner/Dockerfile.dev

@@ -1,7 +1,8 @@
-FROM golang:1.22.6-bullseye
+FROM golang:1.22.6-alpine
 RUN go install github.com/bokwoon95/wgo@latest
 RUN go install github.com/swaggo/swag/cmd/swag@latest
-RUN apt-get update -y; apt-get install -y ffmpeg libchromaprint-tools libchromaprint-dev libfftw3-dev
+
+RUN apk update && apk upgrade && apk add ffmpeg chromaprint mailcap 
 WORKDIR /app
 
 CMD ["wgo", "-xdir", "./app/docs", "swag", "init", "-d", "app", "-o", "./app/docs", "::", "go", "run", "./app"]

scanner/internal/illustration/thumbnail.go

@@ -3,18 +3,113 @@ package illustration
 import (
 	"bytes"
 	"fmt"
-
+	"github.com/kpango/glg"
 	"github.com/u2takey/ffmpeg-go"
+	"strings"
 )
 
+type CropDimensions struct {
+	width  int
+	height int
+	x      int
+	y      int
+}
+
 func GetFrame(filepath string, timestamp int64) ([]byte, error) {
 	formattedDuration := fmt.Sprintf("%.2d:%.2d:%.2d", int(timestamp/3600), (timestamp/60)%60, timestamp%60)
-	buf := bytes.NewBuffer(nil)
-	err := ffmpeg_go.Input(filepath, ffmpeg_go.KwArgs{"ss": formattedDuration}).
+	thumbnail := bytes.NewBuffer(nil)
+	filters := []string{
+		"scale='max(iw,iw*sar)':'max(ih,ih/sar)'",
+		"select=gte(n\\,1)",
+	}
+
+	cmd := ffmpeg_go.Input(filepath, ffmpeg_go.KwArgs{"ss": formattedDuration}).
+		Silent(true).
+		Output("pipe:", ffmpeg_go.KwArgs{
+			"vframes": 1,
+			"format":  "image2",
+			"vcodec":  "mjpeg",
+			"vf":      strings.Join(filters, ", ")}).
+		WithOutput(thumbnail)
+	err := cmd.Run()
+	if err != nil {
+		glg.Error(err)
+		return nil, err
+	}
+	thumbnailBytes := thumbnail.Bytes()
+	croppedThumbnail, _ := RemoveBlackBars(&thumbnailBytes)
+	if croppedThumbnail != nil {
+		return croppedThumbnail.Bytes(), nil
+	}
+	return thumbnailBytes, err
+}
+
+func RemoveBlackBars(frame *[]byte) (*bytes.Buffer, error) {
+
+	crops, err := GetCropDimensions(bytes.NewBuffer(*frame))
+	if err != nil || crops == nil {
+		if err != nil {
+			glg.Error(err)
+		}
+		return nil, err
+	}
+	newFrame := bytes.NewBuffer(nil)
+	err = ffmpeg_go.Input("pipe:", ffmpeg_go.KwArgs{"format": "image2pipe"}).
+		Filter("crop", ffmpeg_go.Args{fmt.Sprintf("%d:%d:%d:%d", crops.width, crops.height, crops.x, crops.y)}).
+		Output("pipe:", ffmpeg_go.KwArgs{
+			"format":  "image2",
+			"vframes": "1",
+			"vcodec":  "mjpeg"}).
+		WithInput(bytes.NewBuffer(*frame)).
+		WithOutput(newFrame).Run()
+	if err != nil {
+		glg.Error(err)
+		return nil, err
+	}
+	return newFrame, err
+}
+
+func GetCropDimensions(thumbnail *bytes.Buffer) (*CropDimensions, error) {
+
+	rawout := bytes.NewBuffer(nil)
+
+	err := ffmpeg_go.Input("pipe:", ffmpeg_go.KwArgs{"f": "image2pipe", "loop": "1"}).
 		Silent(true).
-		Filter("scale", ffmpeg_go.Args{"'max(iw,iw*sar)':'max(ih,ih/sar)'"}).
-		Filter("select", ffmpeg_go.Args{"gte(n,1)"}).
-		Output("pipe:", ffmpeg_go.KwArgs{"vframes": 1, "format": "image2", "vcodec": "mjpeg"}).
-		WithOutput(buf).Run()
-	return buf.Bytes(), err
+		Output("pipe:", ffmpeg_go.KwArgs{
+			"f":        "null",
+			"frames:v": "3",
+			"vf":       "cropdetect=limit=0:round=0"}).
+		WithErrorOutput(rawout).
+		WithInput(thumbnail).
+		WithOutput(rawout).Run()
+	if err != nil {
+		glg.Error(err)
+		return nil, err
+	}
+	strout := string((*rawout).Bytes())
+	lines := strings.Split(strout, "\n")
+	lineCount := len(lines)
+	if lineCount == 0 {
+		return nil, nil
+	}
+	for index := lineCount; index > 0; index-- {
+		token := "crop="
+		line := lines[index-1]
+		cropPos := strings.Index(line, token)
+		if cropPos == -1 {
+			continue
+		}
+		dims := CropDimensions{}
+		_, err = fmt.Sscanf(line[cropPos+len(token):], "%d:%d:%d:%d",
+			&dims.width, &dims.height, &dims.x, &dims.y)
+		if err != nil {
+			glg.Error(err)
+			continue
+		}
+		if dims.width < 0 || dims.height < 0 {
+			continue
+		}
+		return &dims, nil
+	}
+	return nil, nil
 }