Blank output image (v1.3) about aggdraw

[djhoese]

What version of python and what operating system? Thanks.

[bhbr]

python 2.7.14 on macOS Sierra

[djhoese]

With the old version of aggdraw is this what the result looked like for you (this is Python 3.6, OSX High Sierra):

[bhbr]

Yes.
I'll see if the issue persists with Python 3. If not, all the more reason to migrate

[bhbr]

The bug does not appear with Python 3.6.

[djhoese]

What if you don't use any alpha (RGB instead of RGBA) when running it in python 2? I've been told by more experienced users (I just maintain the code) that aggdraw has always had less than ideal handling of alpha.

[bhbr]

Without alpha (I presume you mean making the array MxNx3 and mode = "RGB") the bug appears with both Python 2 and 3.

[djhoese]

@bhbr I'm just now reviewing this code and I'm a little confused by what is happening. The way you are creating a Draw object, flushing it, then using the original pixel_array to make a new image, is this advertised/accepted behavior for aggdraw? Is the expectation that pixel_array will get written to in-place through the Image object? Or am I looking at this too early in the morning and misunderstanding something?

[burlito]

Hi,

I just hit on this bug while trying https://github.com/3b1b/manim. I bisected library and it looks like it's because of commit 1832993, I did also try your reproducer with and without commit and it seems to be hitting same thing.

I hope it helped.

[burlito]

So what I think is happening is:

in static agg::rgba8 getcolor(PyObject* color, int opacity) https://github.com/pytroll/aggdraw/blob/master/aggdraw.cxx#L896

in if statement PyBytes_Check(color) was changed to PyUnicode_Check(color) which is false in situations where PyBytes_Check was true.

next even if you skip that PyObject* ascii_color = PyUnicode_AsASCIIString(color); will always give you NULL.

I don't think PyUnicode_Check and PyUnicode_AsASCIIString are used corectly in that file

[djhoese]

Awesome @burlito thanks for the help. I agree it looks like I screwed up the python 2 support. There should be a second else if statement to check for the bytes.

For your second point, what do you mean PyUnicode_AsASCIIString will always return NULL? In both python 2 and 3 that should convert a unicode object to an ascii string if it can be converted (https://docs.python.org/3/c-api/unicode.html#c.PyUnicode_AsASCIIString). As mentioned the code should have another if statement for bytes and then run PyBytes_AsString(color). You are right that the PyUnicode_AsASCIIString will always return NULL for a bytes object (if it doesn't crash), but that function shouldn't be called in that case.

I'll see if I can find time to test this later.

[djhoese]

I have this fixed locally, but it seems a test is failing on python 2 now and I can't get it to pass even after removing my changes. This should be fun.