ffimage/ffmpeg_command.go at master · teacat/ffimage · GitHub

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package ffimage

import (
	"strconv"
	"strings"
)

func (i *Image) buildFFmpegArgs(outputPath string, outputFormat ImageFormat) []string {
	args := []string{"-i", i.Path}
	filters := strings.Join(i.output.filters, ",")

	switch outputFormat {
	case ImageFormatGIF:
		filterGraph := "[0:v]" + filters + ",split=2[gif_source][palette_source];" +
			"[palette_source]palettegen[palette];" +
			"[gif_source][palette]paletteuse[output]"
		args = append(args, "-filter_complex", filterGraph, "-map", "[output]")
	case ImageFormatAVIF:
		filterGraph := "[0:v]" + filters + ",split=2[rgb][alpha_source];" +
			"[alpha_source]alphaextract[alpha];" +
			"[rgb]format=rgba[color];" +
			"[color][alpha]alphamerge[merged];" +
			"[merged]format=yuva420p[yuva];" +
			"[yuva]split=2[output_color][output_alpha_source];" +
			"[output_alpha_source]alphaextract[output_alpha]"
		args = append(args,
			"-filter_complex", filterGraph,
			"-map", "[output_color]",
			"-map", "[output_alpha]",
		)
	default:
		if filters != "" {
			args = append(args, "-vf", filters)
		}
	}

	args = append(args, "-map_metadata", "-1")
	args = append(args, i.output.customArgs...)
	if i.output.framerate != nil {
		args = append(args, "-r", strconv.Itoa(*i.output.framerate))
	}
	if i.output.dropFrames {
		args = append(args, "-vframes", "1")
	}

	if i.output.quality != 0 {
		switch outputFormat {
		case ImageFormatAVIF:
			quality := qualityFactor(0, 63, i.output.quality, true)
			args = append(args, "-crf", strconv.Itoa(quality))
		case ImageFormatJPEG:
			quality := qualityFactor(2, 31, i.output.quality, true)
			args = append(args, "-qscale:v", strconv.Itoa(quality))
		case ImageFormatJPEGXL:
			quality := qualityFactor(0, 100, i.output.quality, false)
			args = append(args, "-qscale:v", strconv.Itoa(quality))
		case ImageFormatWEBP:
			quality := qualityFactor(0, 100, i.output.quality, false)
			args = append(args, "-quality", strconv.Itoa(quality))
		}
	}

	if outputFormat == ImageFormatAPNG {
		args = append(args, "-plays", strconv.Itoa(i.output.loop))
	} else {
		args = append(args, "-loop", strconv.Itoa(i.output.loop))
	}

	if outputFormat == ImageFormatAVIF {
		if i.output.dropFrames || i.singleFrame {
			args = append(args,
				"-frames:v:0", "1",
				"-frames:v:1", "1",
				"-still-picture", "1",
			)
		} else if i.output.framerate == nil {
			args = append(args, "-fps_mode", "passthrough")
		}
	}

	args = append(args, outputPath, "-y")
	return args
}