DataURI: fix introduced bug: if original data URI is shorter, use the…

… original and not the decoded, related to #282

common.go

@@ -36,6 +36,7 @@ func Mediatype(b []byte) []byte {
 
 // DataURI minifies a data URI and calls a minifier by the specified mediatype. Specifications: https://www.ietf.org/rfc/rfc2397.txt.
 func DataURI(m *M, dataURI []byte) []byte {
+	origData := parse.Copy(dataURI)
 	mediatype, data, err := parse.DataURI(dataURI)
 	if err != nil {
 		return dataURI
@@ -52,8 +53,8 @@ func DataURI(m *M, dataURI []byte) []byte {
 			break
 		}
 	}
-	if len(dataURI) < base64Len && len(dataURI) < asciiLen {
-		return dataURI
+	if len(origData) < base64Len && len(origData) < asciiLen {
+		return origData
 	}
 	if base64Len < asciiLen {
 		encoded := make([]byte, base64Len-len(";base64"))

common_test.go

@@ -48,7 +48,7 @@ func TestDataURI(t *testing.T) {
 		{"data:text/x,<?xx?>", "data:text/x,%3C%3Fxx%3F%3E"},
 		{"data:text/other,\"<\u2318", "data:text/other,%22%3C%E2%8C%98"},
 		{"data:text/other,\"<\u2318>", "data:text/other;base64,IjzijJg+"},
-		{`data:text/svg+xml,<svg height="100" width="100"><circle cx="50" cy="50" r="40" stroke="black" stroke-width="3" fill="red" /></svg>`, `data:text/svg+xml,<svg height="100" width="100"><circle cx="50" cy="50" r="40" stroke="black" stroke-width="3" fill="red" /></svg>`},
+		{`data:text/svg+xml,%3Csvg height="100" width="100"><circle cx="50" cy="50" r="40" stroke="black" stroke-width="3" fill="red" /></svg>`, `data:text/svg+xml,%3Csvg height="100" width="100"><circle cx="50" cy="50" r="40" stroke="black" stroke-width="3" fill="red" /></svg>`},
 	}
 	m := New()
 	m.AddFunc("text/x", func(_ *M, w io.Writer, r io.Reader, _ map[string]string) error {