feat: add built-in gif converter

Signed-off-by: Thanh Thai <[email protected]>

internal/converter.go

@@ -5,6 +5,7 @@ import (
 	"github.com/disintegration/imaging"
 	ffmpeg "github.com/u2takey/ffmpeg-go"
 	"image"
+	"image/gif"
 	"image/jpeg"
 	_ "image/png"
 	"os"
@@ -102,6 +103,52 @@ func ConvertDynamic(inputPath, outputDir, outputExt, tmpDir string) error {
 	return nil
 }
 
+func ConvertGif(inputPath, outputDir, outputExt string, jpegQuality int) error {
+	// open input file
+	inputFile, err := os.Open(inputPath)
+	if err != nil {
+		return fmt.Errorf("error opening input file: %w", err)
+	}
+	defer func(file *os.File) {
+		err = file.Close()
+		if err != nil {
+			logger.Error("error closing input file", err)
+		}
+	}(inputFile)
+
+	// decode gif
+	gifData, err := gif.DecodeAll(inputFile)
+	if err != nil {
+		return fmt.Errorf("error decoding gif: %w", err)
+	}
+
+	// create output file
+	outputFile, err := os.Create(generateOutput(inputPath, outputDir, outputExt))
+	if err != nil {
+		logger.Fatal("error creating output file", err)
+	}
+	defer func(outputFile *os.File) {
+		err = outputFile.Close()
+		if err != nil {
+			logger.Error("error closing output file", err)
+		}
+	}(outputFile)
+
+	// loop through gif frames
+	for _, frame := range gifData.Image {
+		// resizing frame
+		img := imaging.Resize(frame, 128, 128, imaging.Lanczos)
+
+		// encode img to output file
+		err = jpeg.Encode(outputFile, img, &jpeg.Options{Quality: jpegQuality})
+		if err != nil {
+			return fmt.Errorf("error encoding image: %w", err)
+		}
+	}
+
+	return nil
+}
+
 func generateOutput(inputPath, outputDir, outputExt string) string {
 	inputBase := filepath.Base(inputPath)
 	inputExt := filepath.Ext(inputPath)

internal/converter_test.go

@@ -12,13 +12,13 @@ import (
 )
 
 const (
-	testImage           = "test.png"
-	testGif             = "test.gif"
-	testVideo           = "test.mp4"
-	outputDir           = "outputs_test"
-	outputStaticExt     = "jpg"
-	outputDynamicExt    = "mjpeg"
-	outputStaticQuality = 95
+	testImage         = "test.png"
+	testGif           = "test.gif"
+	testVideo         = "test.mp4"
+	outputDir         = "outputs_test"
+	outputStaticExt   = "jpg"
+	outputDynamicExt  = "mjpeg"
+	outputJpegQuality = 95
 )
 
 func TestConvertStatic(t *testing.T) {
@@ -58,7 +58,7 @@ func TestConvertStatic(t *testing.T) {
 	}
 
 	// convert static media
-	err = ConvertStatic(testFile.Name(), outputDir, outputStaticExt, outputStaticQuality)
+	err = ConvertStatic(testFile.Name(), outputDir, outputStaticExt, outputJpegQuality)
 	if err != nil {
 		t.Errorf("error converting image: %v", err)
 		t.FailNow()
@@ -285,6 +285,89 @@ func TestConvertDynamicVideo(t *testing.T) {
 	}
 }
 
+func TestConvertGif(t *testing.T) {
+	// prepare test file
+	img := image.NewRGBA(image.Rect(0, 0, 512, 512))
+	for y := 0; y < img.Bounds().Dy(); y++ {
+		for x := 0; x < img.Bounds().Dx(); x++ {
+			img.Set(x, y, color.RGBA{})
+		}
+	}
+
+	// create test file
+	testFile, err := os.Create(testGif)
+	if err != nil {
+		panic(err)
+	}
+	defer func(file *os.File) {
+		err = file.Close()
+		if err != nil {
+			t.Logf("error closing test gif: %v", err)
+		}
+		err = os.Remove(file.Name())
+		if err != nil {
+			t.Logf("error removing test gif: %v", err)
+		}
+	}(testFile)
+
+	// encode test gif
+	if err = gif.Encode(testFile, img, nil); err != nil {
+		panic(err)
+	}
+
+	// create output directory
+	err = os.MkdirAll(outputDir, 0755)
+	if err != nil {
+		panic(err)
+	}
+
+	// convert gif
+	err = ConvertGif(testFile.Name(), outputDir, outputDynamicExt, outputJpegQuality)
+	if err != nil {
+		t.Errorf("error converting gif: %v", err)
+		t.FailNow()
+	}
+
+	// check if the output file exist
+	outputPath := generateOutput(testVideo, outputDir, outputDynamicExt)
+	defer func(path string) {
+		err = os.RemoveAll(path)
+		if err != nil {
+			t.Logf("error removing output directory: %v", err)
+		}
+	}(outputDir)
+	if _, err = os.Stat(outputPath); os.IsNotExist(err) {
+		t.Errorf("output file was not created")
+		t.FailNow()
+	}
+
+	// open output file
+	outputFile, err := os.Open(outputPath)
+	if err != nil {
+		t.Errorf("error opening output file: %v", err)
+		t.FailNow()
+	}
+	defer func(file *os.File) {
+		err = file.Close()
+		if err != nil {
+			t.Logf("error closing output file: %v", err)
+			t.FailNow()
+		}
+	}(outputFile)
+
+	// decode output file
+	config, _, err := image.DecodeConfig(outputFile)
+	if err != nil {
+		t.Errorf("error decoding output file: %v", err)
+		t.FailNow()
+	}
+
+	// check output file dimensions
+	if config.Width != 128 || config.Height != 128 {
+		t.Errorf("output gif dimensions is incorrect, got: %dx%d, want: 128x128", config.Width, config.Height)
+	}
+}
+
 func TestGenerateOutput(t *testing.T) {
 	outputPath := generateOutput(testImage, outputDir, outputStaticExt)