Change to ValueError when encoding an empty image

Author: radarhere

Tests/test_file_jpeg.py

@@ -85,7 +85,7 @@ def test_sanity(self) -> None:
     def test_zero(self, size: tuple[int, int], tmp_path: Path) -> None:
         f = tmp_path / "temp.jpg"
         im = Image.new("RGB", size)
-        with pytest.raises(ValueError):
+        with pytest.raises(ValueError, match="cannot write empty image"):
             im.save(f)
 
     def test_app(self) -> None:

Tests/test_file_libtiff.py

@@ -1244,7 +1244,7 @@ def test_save_single_strip(
     def test_save_zero(self, compression: str | None, tmp_path: Path) -> None:
         im = Image.new("RGB", (0, 0))
         out = tmp_path / "temp.tif"
-        with pytest.raises(SystemError):
+        with pytest.raises(ValueError, match="cannot write empty image"):
             im.save(out, compression=compression)
 
     def test_save_many_compressed(self, tmp_path: Path) -> None:

src/PIL/JpegImagePlugin.py

@@ -661,10 +661,6 @@ def get_sampling(im: Image.Image) -> int:
 
 
 def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
-    if im.width == 0 or im.height == 0:
-        msg = "cannot write empty image as JPEG"
-        raise ValueError(msg)
-
     try:
         rawmode = RAWMODE[im.mode]
     except KeyError as e:

src/encode.c

@@ -239,6 +239,10 @@ _setimage(ImagingEncoderObject *encoder, PyObject *args) {
     if (!im) {
         return NULL;
     }
+    if (im->xsize == 0 || im->ysize == 0) {
+        PyErr_SetString(PyExc_ValueError, "cannot write empty image");
+        return NULL;
+    }
 
     encoder->im = im;