Include limit in error message

Author: radarhere

Tests/test_file_webp.py

@@ -163,7 +163,9 @@ def test_write_encoding_error_bad_dimension(self, tmp_path: Path) -> None:
         im = Image.new("L", (16384, 16384))
         with pytest.raises(ValueError) as e:
             im.save(temp_file)
-        assert str(e.value) == "encoding error 5: Image size exceeds WebP limit"
+        assert (
+            str(e.value) == "encoding error 5: Image size exceeds WebP limit of 16383"
+        )
 
     def test_WebPEncode_with_invalid_args(self) -> None:
         """

src/_webp.c

@@ -673,9 +673,11 @@ WebPEncode_wrapper(PyObject *self, PyObject *args) {
     WebPPictureFree(&pic);
     if (!ok) {
         int error_code = (&pic)->error_code;
-        const char *message = "";
+        static char message[50] = "";
         if (error_code == VP8_ENC_ERROR_BAD_DIMENSION) {
-            message = ": Image size exceeds WebP limit";
+            sprintf(
+                message, ": Image size exceeds WebP limit of %d", WEBP_MAX_DIMENSION
+            );
         }
         PyErr_Format(PyExc_ValueError, "encoding error %d%s", error_code, message);
         return NULL;