lottie: add convert functions

Signed-off-by: Sumner Evans <[email protected]>

ffmpeg/convert.go

@@ -68,7 +68,7 @@ func ConvertPath(ctx context.Context, inputFile string, outputExtension string,
 	cmd.Stderr = logWriter
 	err := cmd.Run()
 	if err != nil {
-		return "", fmt.Errorf("ffmpeg error: %+v", err)
+		return "", fmt.Errorf("ffmpeg error: %w", err)
 	}
 
 	if removeInput {

lottie/convert.go

@@ -0,0 +1,103 @@
+// Copyright (c) 2024 Sumner Evans
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package lottie
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"github.com/rs/zerolog"
+	"go.mau.fi/util/exzerolog"
+)
+
+var lottieconverterPath string
+
+func init() {
+	lottieconverterPath, _ = exec.LookPath("lottieconverter")
+}
+
+// Supported returns whether lottieconverter is available on the system.
+//
+// lottieconverter is considered to be available if a binary called
+// lottieconverter is found in $PATH, or if [SetPath] has been called
+// explicitly with a non-empty path.
+func Supported() bool {
+	return lottieconverterPath != ""
+}
+
+// SetPath overrides the path to the lottieconverter binary.
+func SetPath(path string) {
+	lottieconverterPath = path
+}
+
+// ConvertPath converts a lottie file on disk using lottieconverter. The
+// filename will be the same as the input file, but with the extension changed
+// to the format specified.
+//
+// Args:
+//   - inputFile: the full path to the file.
+//   - format: the format to convert to. Either "gif" or "png".
+//   - width: the width of the output file.
+//   - height: the height of the output file.
+//   - extraArgs: additional arguments to pass to lottieconverter.
+//
+// Returns: the path to the converted file.
+func ConvertPath(ctx context.Context, inputFile, format string, width, height int, removeInput bool, extraArgs ...string) (outputFile string, err error) {
+	outputFile = strings.TrimSuffix(strings.TrimSuffix(inputFile, filepath.Ext(inputFile)), "*") + "." + format
+	err = convert(ctx, inputFile, nil, outputFile, nil, format, width, height, extraArgs...)
+	if err != nil {
+		return "", err
+	}
+
+	if removeInput {
+		_ = os.Remove(inputFile)
+	}
+	return outputFile, nil
+}
+
+// ConvertBytes converts lottie data to an [image.Image] using lottieconverter.
+//
+// Args:
+//   - data: the lottie data.
+//   - format: the format to convert to. Either "gif" or "png".
+//   - width: the width of the output file.
+//   - height: the height of the output file.
+//   - extraArgs: additional arguments to pass to lottieconverter.
+//
+// Returns: the path to the converted file.
+func ConvertBytes(ctx context.Context, data []byte, format string, width, height int, extraArgs ...string) (img []byte, err error) {
+	var output bytes.Buffer
+	err = convert(ctx, "-", bytes.NewReader(data), "-", &output, format, width, height, extraArgs...)
+	return output.Bytes(), err
+}
+
+func convert(ctx context.Context, inputFile string, inputReader io.Reader, outputFile string, outputWriter io.Writer, format string, width, height int, extraArgs ...string) error {
+	args := []string{inputFile, outputFile, format, fmt.Sprintf("%dx%d", width, height)}
+	args = append(args, extraArgs...)
+
+	cmd := exec.CommandContext(ctx, lottieconverterPath, args...)
+	ctxLog := zerolog.Ctx(ctx).With().Str("command", "lottieconverter").Logger()
+	logWriter := exzerolog.NewLogWriter(ctxLog).WithLevel(zerolog.WarnLevel)
+	cmd.Stdin = inputReader
+	if outputWriter != nil {
+		cmd.Stdout = outputWriter
+	} else {
+		cmd.Stdout = logWriter
+	}
+	cmd.Stderr = logWriter
+
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("lottieconverter error: %w", err)
+	}
+	return nil
+}