go/img/img.go

package img

import (
	"fmt"
	"image"
	"image/draw"
	"image/png"
	"os"
	"os/exec"

	"github.com/anthonynsimon/bild/adjust"
)

const (
	StyleDark = -0.70

	ffmpegBin = "/usr/bin/ffmpeg"
)

var ErrorFFMPEGBinaryNotFound = fmt.Errorf("ffmpeg binary not found: %s", ffmpegBin)

func CreateThumbnail(videoFile, thumbFilename string) (err error) {
	// ffmpeg -i videoFile -ss 00:00:01.000 -vframes 1 output.png
	cmd := exec.Command(ffmpegBin, "-i", videoFile, "-ss", "00:05:00.000", "-vframes", "1", thumbFilename)
	_, err = cmd.Output()
	if err != nil {
		return ErrorFFMPEGBinaryNotFound
	}
	return nil
}

func Overlay(inputFile, overlayFile string, style float64) (err error) {
	thumb, err := os.Open(inputFile)
	if err != nil {
		return err
	}

	overlay, err := os.Open(overlayFile)
	if err != nil {
		return err
	}

	img0, err := png.Decode(thumb)
	if err != nil {
		return err
	}
	defer thumb.Close()

	img1, err := png.Decode(overlay)
	if err != nil {
		return err
	}
	defer overlay.Close()

	b0 := img0.Bounds()
	b1 := img1.Bounds()

	img0 = adjust.Brightness(img0, style)

	offset := image.Pt(b0.Dx()/2-b1.Dx()/2, b0.Dy()/2-b1.Dy()/2)

	m := image.NewRGBA(b0)
	draw.Draw(m, b0, img0, image.Point{}, draw.Src)
	draw.Draw(m, img1.Bounds().Add(offset), img1, image.Point{}, draw.Over)

	imgw, err := os.Create(inputFile)
	if err != nil {
		return err
	}

	png.Encode(imgw, m)
	defer imgw.Close()

	return nil
}