The value in the coordinates list cannot exceed 32767.

[zhanbao2000]

In my project, I need to draw an image with a large size. But when I used the line method, I found that some lines could not be drawn. After testing, I found that if the value of coordinate of a point in the list of coordinates (both horizontal and vertical) exceeds 32767, then the line method will not draw the line, while Pillow does.

I have used the following code for testing.

from aggdraw import Draw, Pen
from PIL import Image, ImageDraw

im = Image.new('RGB', (40000, 1000), 'white')

# No problem when using Pillow, which draws a horizontal bar up to 40000 pixels long.
draw = ImageDraw.Draw(im)
draw.line((0, 250, 40000, 250), fill='red', width=500)

# This line cannot be drawn unless I change this value to 32767 or less.
draw2 = Draw(im)
pen = Pen(color=(0, 0, 255), width=500)
draw2.line((0, 750, 32768, 750), pen)
draw2.flush()

im.show()

In addition, this problem occurs in other methods that require a list of coordinates to be entered (such as path).

• Windows 10
• Python: 3.10
• Pillow: 9.1.1
• aggdraw: 1.3.15

[djhoese]

So 32767 is the maximum value of a 16-bit signed integer. As far as I can tell all the path information for creating a line is stored in this class from the agg C++ library:

https://github.com/pytroll/aggdraw/blob/maint/1.3/agg2/include/agg_path_storage.h

As far as I can tell this class uses unsigned which is a 16-bit unsigned integer and it only does that for number of vertices (as far as I can tell) not the value of the vertex coordinates. So I'm not really sure where the 16-bit limit is happening.

Either way, I'm afraid that unless this can be tracked down to something in aggdraw.cxx, this is likely a major limitation of the agg C++ library and would require essentially rewriting portions of agg. I can't say for sure what would need to be changed as I haven't tracked down where this limit is happening. Note that the current version of agg in the main branch is newer than the version in the maint/1.3 branch and main has not had a public release yet.