Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit62a96ff

Browse files
committed
TST: Calculate RMS and diff image in C++
The current implementation is not slow, but uses a lot of memory perimage.In `compare_images`, we have:- one actual and one expected image as uint8 (2×image)- both converted to int16 (though original is thrown away) (4×)which adds up to 4× the image allocated in this function.Then it calls `calculate_rms`, which has:- a difference between them as int16 (2×)- the difference cast to 64-bit float (8×)- the square of the difference as 64-bit float (though possibly the original difference was thrown away) (8×)which at its peak has 16× the image allocated in parallel.If the RMS is over the desired tolerance, then `save_diff_image` iscalled, which:- loads the actual and expected images _again_ as uint8 (2× image)- converts both to 64-bit float (throwing away the original) (16×)- calculates the difference (8×)- calculates the absolute value (8×)- multiples that by 10 (in-place, so no allocation)- clips to 0-255 (8×)- casts to uint8 (1×)which at peak uses 32× the image.So at their peak, `compare_images`→`calculate_rms` will have 20× theimage allocated, and then `compare_images`→`save_diff_image` will have36× the image allocated. This is generally not a problem, but onresource-constrained places like WASM, it can sometimes run out ofmemory just in `calculate_rms`.This implementation in C++ always allocates the diff image, even whennot needed, but doesn't have all the temporaries, so it's a maximum of3× the image size (plus a few scalar temporaries).
1 parent38a8e15 commit62a96ff

File tree

2 files changed

+79
-9
lines changed

2 files changed

+79
-9
lines changed

‎lib/matplotlib/testing/compare.py

Lines changed: 4 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -19,7 +19,7 @@
1919
fromPILimportImage
2020

2121
importmatplotlibasmpl
22-
frommatplotlibimportcbook
22+
frommatplotlibimportcbook,_image
2323
frommatplotlib.testing.exceptionsimportImageComparisonFailure
2424

2525
_log=logging.getLogger(__name__)
@@ -398,7 +398,7 @@ def compare_images(expected, actual, tol, in_decorator=False):
398398
399399
The two given filenames may point to files which are convertible to
400400
PNG via the `.converter` dictionary. The underlying RMS is calculated
401-
with the `.calculate_rms` function.
401+
in a similar way to the `.calculate_rms` function.
402402
403403
Parameters
404404
----------
@@ -469,17 +469,12 @@ def compare_images(expected, actual, tol, in_decorator=False):
469469
ifnp.array_equal(expected_image,actual_image):
470470
returnNone
471471

472-
# convert to signed integers, so that the images can be subtracted without
473-
# overflow
474-
expected_image=expected_image.astype(np.int16)
475-
actual_image=actual_image.astype(np.int16)
476-
477-
rms=calculate_rms(expected_image,actual_image)
472+
rms,abs_diff=_image.calculate_rms_and_diff(expected_image,actual_image)
478473

479474
ifrms<=tol:
480475
returnNone
481476

482-
save_diff_image(expected,actual,diff_image)
477+
Image.fromarray(abs_diff).save(diff_image,format="png")
483478

484479
results=dict(rms=rms,expected=str(expected),
485480
actual=str(actual),diff=str(diff_image),tol=tol)

‎src/_image_wrapper.cpp

Lines changed: 75 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,8 @@
11
#include<pybind11/pybind11.h>
22
#include<pybind11/numpy.h>
33

4+
#include<algorithm>
5+
46
#include"_image_resample.h"
57
#include"py_converters.h"
68

@@ -200,6 +202,76 @@ image_resample(py::array input_array,
200202
}
201203

202204

205+
// This is used by matplotlib.testing.compare to calculate RMS and a difference image.
206+
static py::tuple
207+
calculate_rms_and_diff(py::array_t<unsignedchar> expected_image,
208+
py::array_t<unsignedchar> actual_image)
209+
{
210+
if (expected_image.ndim() !=3) {
211+
auto exceptions =py::module_::import("matplotlib.testing.exceptions");
212+
auto ImageComparisonFailure = exceptions.attr("ImageComparisonFailure");
213+
py::set_error(
214+
ImageComparisonFailure,
215+
"Expected image must be 3-dimensional, but is {ndim}-dimensional"_s.format(
216+
"ndim"_a=expected_image.ndim()));
217+
throwpy::error_already_set();
218+
}
219+
220+
if (actual_image.ndim() !=3) {
221+
auto exceptions =py::module_::import("matplotlib.testing.exceptions");
222+
auto ImageComparisonFailure = exceptions.attr("ImageComparisonFailure");
223+
py::set_error(
224+
ImageComparisonFailure,
225+
"Actual image must be 3-dimensional, but is {ndim}-dimensional"_s.format(
226+
"ndim"_a=actual_image.ndim()));
227+
throwpy::error_already_set();
228+
}
229+
230+
auto height = expected_image.shape(0);
231+
auto width = expected_image.shape(1);
232+
auto depth = expected_image.shape(2);
233+
234+
if (height != actual_image.shape(0) || width != actual_image.shape(1) ||
235+
depth != actual_image.shape(2)) {
236+
auto exceptions =py::module_::import("matplotlib.testing.exceptions");
237+
auto ImageComparisonFailure = exceptions.attr("ImageComparisonFailure");
238+
py::set_error(
239+
ImageComparisonFailure,
240+
"Image sizes do not match expected size: {expected_image.shape}"_s
241+
"actual size {actual_image.shape}"_s.format(
242+
"expected_image"_a=expected_image,"actual_image"_a=actual_image));
243+
throwpy::error_already_set();
244+
}
245+
auto expected = expected_image.unchecked<3>();
246+
auto actual = actual_image.unchecked<3>();
247+
248+
py::ssize_t diff_dims[3] = {height, width,3};
249+
py::array_t<unsignedchar>diff_image(diff_dims);
250+
auto diff = diff_image.mutable_unchecked<3>();
251+
252+
double total =0.0;
253+
for (auto i =0; i < height; i++) {
254+
for (auto j =0; j < width; j++) {
255+
for (auto k =0; k < depth; k++) {
256+
auto pixel_diff =static_cast<double>(expected(i, j, k)) -
257+
static_cast<double>(actual(i, j, k));
258+
259+
total += pixel_diff*pixel_diff;
260+
261+
if (k !=3) {// Hard-code a fully solid alpha channel by omitting it.
262+
diff(i, j, k) =static_cast<unsignedchar>(std::clamp(
263+
abs(pixel_diff) *10,// Expand differences in luminance domain.
264+
0.0,255.0));
265+
}
266+
}
267+
}
268+
}
269+
total = total / (width * height * depth);
270+
271+
returnpy::make_tuple(sqrt(total), diff_image);
272+
}
273+
274+
203275
PYBIND11_MODULE(_image, m, py::mod_gil_not_used())
204276
{
205277
py::enum_<interpolation_e>(m,"_InterpolationType")
@@ -232,4 +304,7 @@ PYBIND11_MODULE(_image, m, py::mod_gil_not_used())
232304
"norm"_a =false,
233305
"radius"_a =1,
234306
image_resample__doc__);
307+
308+
m.def("calculate_rms_and_diff", &calculate_rms_and_diff,
309+
"expected_image"_a,"actual_image"_a);
235310
}

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp