add svg output support, but only with primitive

data.go

@@ -19,6 +19,7 @@ const (
 	optFlipHorizontal  = "fh"
 	optFormatJPEG      = "jpeg"
 	optFormatPNG       = "png"
+	optFormatSVG       = "svg"
 	optFormatTIFF      = "tiff"
 	optPrimitivePrefix = "p"
 	optRotatePrefix    = "r"
@@ -70,7 +71,7 @@ type Options struct {
 	// will always be overwritten by the value of Proxy.ScaleUp.
 	ScaleUp bool
 
-	// Desired image format. Valid values are "jpeg", "png", "tiff".
+	// Desired image format. Valid values are "jpeg", "png", "svg", "tiff".
 	Format string
 
 	// Crop rectangle params
@@ -256,7 +257,7 @@ func ParseOptions(str string) Options {
 			options.FlipHorizontal = true
 		case opt == optScaleUp: // this option is intentionally not documented above
 			options.ScaleUp = true
-		case opt == optFormatJPEG, opt == optFormatPNG, opt == optFormatTIFF:
+		case opt == optFormatJPEG, opt == optFormatPNG, opt == optFormatSVG, opt == optFormatTIFF:
 			options.Format = opt
 		case opt == optSmartCrop:
 			options.SmartCrop = true

imageproxy.go

@@ -263,6 +263,9 @@ func peekContentType(p *bufio.Reader) string {
 	if err != nil && err != bufio.ErrBufferFull && err != io.EOF {
 		return ""
 	}
+	if bytes.HasPrefix(byt, []byte("<svg")) {
+		return "image/svg+xml"
+	}
 	return http.DetectContentType(byt)
 }
 

transform.go

@@ -65,6 +65,11 @@ func Transform(img []byte, opt Options) ([]byte, error) {
 		format = "jpeg"
 	}
 
+	if opt.Format == "svg" && opt.Primitive.Count == 0 {
+		// svg output only supported with primitive transform
+		opt.Format = ""
+	}
+
 	if opt.Format != "" {
 		format = opt.Format
 	}
@@ -109,6 +114,12 @@ func Transform(img []byte, opt Options) ([]byte, error) {
 		if err != nil {
 			return nil, err
 		}
+	case "svg":
+		o := opt // copy
+		o.Primitive.Count = 0
+		m = transformImage(m, o)
+		model := transformPrimitive(m, opt)
+		buf.WriteString(model.SVG())
 	default:
 		return nil, fmt.Errorf("unsupported format: %v", format)
 	}