Add tp_richcompare handler for Imaging_Type/ImagingCore

Tests/test_lib_image.py

@@ -1,7 +1,37 @@
+import secrets
+
 import pytest
 
 from PIL import Image
 
+mode_names_not_bgr = (
+    "1",
+    "L",
+    "LA",
+    "La",
+    "P",
+    "PA",
+    "F",
+    "I",
+    "I;16",
+    "I;16L",
+    "I;16B",
+    "I;16N",
+    "RGB",
+    "RGBA",
+    "RGBa",
+    "RGBX",
+    # Image.frombytes() doesn't work with BGR modes:
+    # unknown raw mode for given image mode
+    # "BGR;15",
+    # "BGR;16",
+    # "BGR;24",
+    "CMYK",
+    "YCbCr",
+    "HSV",
+    "LAB",
+)
+
 
 def test_setmode():
     im = Image.new("L", (1, 1), 255)
@@ -30,3 +60,69 @@
         im.im.setmode("L")
     with pytest.raises(ValueError):
         im.im.setmode("RGBABCDE")
+
+
+@pytest.mark.parametrize("mode", mode_names_not_bgr)
+def test_equal(mode):
+    num_img_bytes = len(Image.new(mode, (2, 2)).tobytes())
+    # alternatively, random.randbytes() in Python 3.9
+    data = secrets.token_bytes(num_img_bytes)
+    img_a = Image.frombytes(mode, (2, 2), data)
+    img_b = Image.frombytes(mode, (2, 2), data)
+    assert img_a.tobytes() == img_b.tobytes()
+    assert img_a.im == img_b.im
+
+
+# With mode "1" different bytes can map to the same value,
+# so we have to be more specific with the values we use.
+def test_not_equal_mode_1():
+    data_a = data_b = bytes(secrets.choice(b"\x00\xff") for i in range(4))
+    while data_a == data_b:
+        data_b = bytes(secrets.choice(b"\x00\xff") for i in range(4))
+    # We need to use rawmode "1;8" so that each full byte is interpreted as a value
+    # instead of the bits in the bytes being interpreted as values.
+    img_a = Image.frombytes("1", (2, 2), data_a, "raw", "1;8")
+    img_b = Image.frombytes("1", (2, 2), data_b, "raw", "1;8")
+    assert img_a.tobytes() != img_b.tobytes()
+    assert img_a.im != img_b.im
+
+
+@pytest.mark.parametrize("mode", [mode for mode in mode_names_not_bgr if mode != "1"])
+def test_not_equal(mode):
+    num_img_bytes = len(Image.new(mode, (2, 2)).tobytes())
+    # alternatively, random.randbytes() in Python 3.9
+    data_a = data_b = secrets.token_bytes(num_img_bytes)
+    while data_a == data_b:
+        data_b = secrets.token_bytes(num_img_bytes)
+    img_a = Image.frombytes(mode, (2, 2), data_a)
+    img_b = Image.frombytes(mode, (2, 2), data_b)
+    assert img_a.tobytes() != img_b.tobytes()
+    assert img_a.im != img_b.im
+
+
+@pytest.mark.skip(reason="no way to directly set C bytes from Python")
+@pytest.mark.parametrize("mode", ("RGB", "RGBX", "YCbCr", "HSV", "LAB"))
+def test_equal_three_channels_four_bytes(mode):
+    img_a = Image.frombytes("RGBA", (2, 2), b"ABC1DEF2GHI3JKL4")
+    img_b = Image.frombytes("RGBA", (2, 2), b"ABC5DEF6GHI7JKL8")
+    # this only sets the mode in Python, not C
+    img_a.mode = mode
+    img_b.mode = mode
+    assert img_a.tobytes() == b"ABCDEFGHIJKL"
+    assert img_b.tobytes() == b"ABCDEFGHIJKL"
+    # this fails because the C code still thinks the mode is RGBA
+    assert img_a.im == img_b.im
+
+
+@pytest.mark.skip(reason="no way to directly set C bytes from Python")
+@pytest.mark.parametrize("mode", ("LA", "La", "PA"))
+def test_equal_two_channels_four_bytes(mode):
+    img_a = Image.frombytes("RGBA", (2, 2), b"1AB23CD45EF67GH8")
+    img_b = Image.frombytes("RGBA", (2, 2), b"1IJ23KL45MN67OP8")
+    # this only sets the mode in Python, not C
+    img_a.mode = mode
+    img_b.mode = mode
+    assert img_a.tobytes() == b"12345678"
+    assert img_b.tobytes() == b"12345678"
+    # this fails because the C code still thinks the mode is RGBA
+    assert img_a.im == img_b.im

src/PIL/Image.py

@@ -597,14 +597,18 @@ def _dump(self, file=None, format=None, **options):
         return filename
 
     def __eq__(self, other):
-        return (
+        if self is other:
+            return True
+        if not (
             self.__class__ is other.__class__
             and self.mode == other.mode
             and self.size == other.size
             and self.info == other.info
-            and self.getpalette() == other.getpalette()
-            and self.tobytes() == other.tobytes()
-        )
+        ):
+            return False
+        self.load()
+        other.load()
+        return self.im == other.im
 
     def __repr__(self):
         return "<%s.%s image mode=%s size=%dx%d at 0x%X>" % (

src/_imaging.c

@@ -3721,6 +3721,134 @@
     (ssizessizeobjargproc)NULL, /*sq_ass_slice*/
 };
 
+/*
+Returns 0 if all of the pixels are the same, otherwise 1.
+Skips unused bytes based on the given mode.
+*/
+static int
+_compare_pixels(
+    const char *mode, const int ysize, const int linesize,
+    const UINT8 **pixels_a, const UINT8 **pixels_b
+) {
+    // Fortunately, all of the modes that have extra bytes in their pixels use four bytes for their pixels.
+    UINT32 mask = 0xffffffff;
+    if (
+        !strcmp(mode, "RGB") || !strcmp(mode, "RGBX") ||
+        !strcmp(mode, "YCbCr") || !strcmp(mode, "HSV") || !strcmp(mode, "LAB")
+    ) {
+        // These modes have three channels in four bytes,
+        // so we have to ignore the last byte.
+        mask ^= 0xff;
+    } else if (!strcmp(mode, "LA") || !strcmp(mode, "La") || !strcmp(mode, "PA")) {
+        // These modes have two channels in four bytes,
+        // so we have to ignore the middle two bytes.
+        mask = 0xff0000ff;
+    }
+
+    if (mask == 0xffffffff) {
+        // If we aren't masking anything we can use memcmp.
+        int y;
+        for (y = 0; y < ysize; y++) {
+            if (memcmp(pixels_a[y], pixels_b[y], linesize)) {
+                return 1;
+            }
+        }
+    } else {
+        const int xsize = linesize / 4;
+        int y, x;
+        for (y = 0; y < ysize; y++) {
+            UINT32 *line_a = (UINT32*)pixels_a[y];
+            UINT32 *line_b = (UINT32*)pixels_b[y];
+            for (x = 0; x < xsize; x++, line_a++, line_b++) {
+                if ((*line_a & mask) != (*line_b & mask)) {
+                    return 1;
+                }
+            }
+        }
+    }
+    return 0;
+}
+
+static PyObject *
+image_richcompare(const ImagingObject *self, const PyObject *other, const int op) {
+    if (op != Py_EQ && op != Py_NE) {
+        Py_RETURN_NOTIMPLEMENTED;
+    }
+
+    // If the other object is not an ImagingObject.
+    if (!PyImaging_Check(other)) {
+        if (op == Py_EQ) {
+            Py_RETURN_FALSE;
+        } else {
+            Py_RETURN_TRUE;
+        }
+    }
+
+    const Imaging img_a = self->image;
+    const Imaging img_b = ((ImagingObject*)other)->image;
+
+    if (
+        strcmp(img_a->mode, img_b->mode)
+        || img_a->xsize != img_b->xsize
+        || img_a->ysize != img_b->ysize
+    ) {
+        if (op == Py_EQ) {
+            Py_RETURN_FALSE;
+        } else {
+            Py_RETURN_TRUE;
+        }
+    }
+
+    const ImagingPalette palette_a = img_a->palette;
+    const ImagingPalette palette_b = img_b->palette;
+    if (palette_a || palette_b) {
+        const UINT8 *palette_a_data = palette_a->palette;
+        const UINT8 *palette_b_data = palette_b->palette;
+        const UINT8 **palette_a_data_ptr = &palette_a_data;
+        const UINT8 **palette_b_data_ptr = &palette_b_data;
+        if (
+            !palette_a || !palette_b
+            || palette_a->size != palette_b->size
+            || strcmp(palette_a->mode, palette_b->mode)
+            || _compare_pixels(
+                palette_a->mode,
+                1,
+                palette_a->size * 4,
+                palette_a_data_ptr,
+                palette_b_data_ptr
+            )
+        ) {
+            if (op == Py_EQ) {
+                Py_RETURN_FALSE;
+            } else {
+                Py_RETURN_TRUE;
+            }
+        }
+    }
+
+    if (
+        _compare_pixels(
+            img_a->mode,
+            img_a->ysize,
+            img_a->linesize,
+            (const UINT8 **)img_a->image,
+            (const UINT8 **)img_b->image
+        )
+    ) {
+        if (op == Py_EQ) {
+            Py_RETURN_FALSE;
+        } else {
+            Py_RETURN_TRUE;
+        }
+    } else {
+        if (op == Py_EQ) {
+            Py_RETURN_TRUE;
+        } else {
+            Py_RETURN_FALSE;
+        }
+    }
+}
+
 /* type description */
 
 static PyTypeObject Imaging_Type = {
@@ -3747,7 +3875,7 @@
     0,                    /*tp_doc*/
     0,                    /*tp_traverse*/
     0,                    /*tp_clear*/
-    0,                    /*tp_richcompare*/
+    (richcmpfunc)image_richcompare, /*tp_richcompare*/
     0,                    /*tp_weaklistoffset*/
     0,                    /*tp_iter*/
     0,                    /*tp_iternext*/