image_probe.go

package ffimage

import (
	"context"
	"encoding/json"
	"fmt"
	"os/exec"
	"strconv"
	"strings"
)

func (i *Image) loadImageSize(c context.Context) error {
	cmd := exec.CommandContext(
		c,
		"ffprobe",
		"-v", "error",
		"-select_streams", "v:0",
		"-show_entries", "stream=width,height,nb_frames",
		"-of", "json",
		i.Path,
	)
	output, err := cmd.Output()
	if err != nil {
		if c.Err() != nil {
			return c.Err()
		}
		if exitError, isExitError := err.(*exec.ExitError); isExitError {
			if ffprobeOutput := strings.TrimSpace(string(exitError.Stderr)); ffprobeOutput != "" {
				return fmt.Errorf("ffprobe output: %w: %s", err, ffprobeOutput)
			}
		}
		return fmt.Errorf("ffprobe output: %w", err)
	}

	probe := struct {
		Streams []struct {
			Width    int    `json:"width"`
			Height   int    `json:"height"`
			NbFrames string `json:"nb_frames"`
		} `json:"streams"`
	}{}
	if err := json.Unmarshal(output, &probe); err != nil {
		return fmt.Errorf("decode ffprobe output: %w", err)
	}
	if len(probe.Streams) == 0 || probe.Streams[0].Width == 0 || probe.Streams[0].Height == 0 {
		return fmt.Errorf("no valid stream found")
	}

	i.sourceWidth = probe.Streams[0].Width
	i.sourceHeight = probe.Streams[0].Height
	i.setWidthHeight(i.sourceWidth, i.sourceHeight)
	frames, err := strconv.Atoi(probe.Streams[0].NbFrames)
	if err == nil && frames > 0 {
		i.frames = frames
		i.singleFrame = frames == 1
		return nil
	}

	i.singleFrame = hasSingleFrame(c, i.Path)
	if err := c.Err(); err != nil {
		return err
	}
	return nil
}

func hasSingleFrame(c context.Context, path string) bool {
	cmd := exec.CommandContext(
		c,
		"ffmpeg",
		"-v", "error",
		"-nostats",
		"-progress", "pipe:1",
		"-i", path,
		"-map", "0:v:0",
		"-frames:v", "2",
		"-f", "null",
		"-",
	)
	output, err := cmd.Output()
	if err != nil {
		return false
	}

	frames := 0
	for _, line := range strings.Split(string(output), "\n") {
		value, found := strings.CutPrefix(strings.TrimSpace(line), "frame=")
		if !found {
			continue
		}
		count, err := strconv.Atoi(strings.TrimSpace(value))
		if err == nil && count > frames {
			frames = count
		}
	}
	return frames == 1
}