computing image axis limits

[Shai Ayal]

Hi all.

Images with a width and/or height of 1 do not display correctly in the
fltk backend as reported in the following bug report:
https://savannah.gnu.org/bugs/?31093

The problem turned out to be bugs with the way image axis limits were
calculated for images where width and/or height was 1.
Axis limits for images are a bit tricky as they have to take the image
pixel size into account. It turns out that today the image pixel size
is be calculated in 4 different places:
1) opengl_renderer::draw_image
2) image::properties:update_{x,y}data
3) image.m: __img__
4) axis.m: __get_tight_lims__

As far as I could see, the calculation in (1) is correct. The attached
patch (not a changeset yet!) fixes a bug in (2) and also adds a small
fix for (3). with it, the following commands:
backend fltk
h=image (ones (1,8));

does not set the axis right, The image is clipped and so nothing shows
up (this can be verified by set (h , "clipping" , "off")).

I am not sure how to approach the fixing of (3) and (4). Maybe we
should consolidate the calculation for 3,4? maybe we should
consolidate 1,2,3,4?

Shai

image1.patch
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