slideshow-api/internal/scale.go

package internal

import (
	"errors"
	"io"
	"os/exec"
	"strings"
	"time"

	"git.velvettear.de/velvettear/loggo"
	"git.velvettear.de/velvettear/slideshow-api/internal/config"
)

// scale an image
func ScaleImage(image string) ([]byte, error) {
	timestamp := time.Now().UnixMilli()
	cmd := exec.Command("convert", image, "-resize", config.Resolution+"^", "-gravity", "center", "-extent", config.Resolution, "-")
	stdout, stdoutError := cmd.StdoutPipe()
	stderr, stderrError := cmd.StderrPipe()
	var data []byte
	cmd.Start()
	if stdoutError != nil {
		return data, stdoutError
	}
	if stderrError != nil {
		return data, stdoutError
	}
	data, stdoutError = io.ReadAll(stdout)
	if stdoutError != nil {
		return data, stdoutError
	}
	errorBytes, stderrError := io.ReadAll(stderr)
	if stderrError != nil {
		return data, stdoutError
	}
	cmd.Wait()
	errorMessage := strings.TrimSpace(string(errorBytes))
	if len(errorMessage) > 0 {
		return data, errors.New(errorMessage)
	}
	loggo.DebugTimed("successfully scaled image", timestamp, "image: "+image, "resolution: "+config.Resolution)
	return data, nil
}