Re: rgbplot composite fails with gnuplot

[Juan Pablo Carbajal]

On Tue, Dec 16, 2014 at 5:27 PM, Juan Pablo Carbajal
<address@hidden> wrote:
> On Tue, Dec 16, 2014 at 5:04 PM, Ben Abbott <address@hidden> wrote:
>>
>>> On Dec 16, 2014, at 10:56 AM, Juan Pablo Carbajal <address@hidden> wrote:
>>>
>>> On Tue, Dec 16, 2014 at 4:32 PM, Juan Pablo Carbajal
>>> <address@hidden> wrote:
>>>> On Tue, Dec 16, 2014 at 4:25 PM, Juan Pablo Carbajal
>>>> <address@hidden> wrote:
>>>>> On Tue, Dec 16, 2014 at 3:31 PM, Ben Abbott <address@hidden> wrote:
>>>>>>> On Dec 16, 2014, at 8:26 AM, Juan Pablo Carbajal <address@hidden> wrote:
>>>>>>>
>>>>>>> Tested in 4.1.0+
>>>>>>> repo id 19402:5cd83b466a3e
>>>>>>>
>>>>>>> octave-cli:1> rgbplot(jet(16),'composite')
>>>>>>>
>>>>>>> multiplot> plot "-" binary array=16x2 scan=yx origin=(1,1) dx=1 dy=0
>>>>>>> using 1 title "" with image; ;
>>>>>>>                                                                 ^
>>>>>>>          line 0: Sample period must be positive. Try `flip` for
>>>>>>> changing direction
>>>>>>>
>>>>>>>
>>>>>>> Can anybody reproduce?
>>>>>>>
>>>>>>> Do we report bugs that involve gnuplot?
>>>>>>>
>>>>>>
>>>>>> I get the same result using gnuplot 4.6 patchlevel 6.
>>>>>>
>>>>>> The error is indicating that dy must be greater than 0.  The m-code 
>>>>>> which produces this gnuplot command is in 
>>>>>> plot/utils/private/__go_draw_axes__.m at lines 554-547.
>>>>>>
>>>>>>        titlespec{data_idx} = "title \"\"";
>>>>>>        usingclause{data_idx} = sprintf ("binary array=%dx%d scan=yx 
>>>>>> origin=(%.15g,%.15g) dx=%.15g dy=%.15g using %s",
>>>>>>            x_dim, y_dim, x_origin, y_origin, dx, dy, format);
>>>>>>        withclause{data_idx} = sprintf ("with %s;", imagetype);
>>>>>>
>>>>>> The image intended looks a similar to a colorbar, so I expect the 
>>>>>> problem is on Octave's end.
>>>>>>
>>>>>> Ben
>>>>>
>>>>> Ben,
>>>>>
>>>>> Ok, thanks. I spotted the problem.
>>>>> It happens when when the data of the image has a single row.
>>>>> That is this fails as well
>>>>>
>>>>> image (1:8)
>>>>>
>>>>> The issue comes in lines 513 and 527-529 of __go_draw_axes__.m
>>>>> When dy=0 because the ydata of the image is [1 1]
>>>>>
>>>>> What are the "dx" and "dy" option for plot in gnuplot? I can't find a
>>>>> reference. Knowing that we jnow how to fix the issue.
>>>>
>>>> Ok, found it.
>>>>
>>>> The clause for gnuplot should not contain "dy=" when dy==0 . This
>>>> makes the plot appear but the axis look wrong.
>>>> So the sprintf command should be conditional on the value of dy.
>>>
>>> Another solution is to leave the sprintf fixed and set dy=1 when line
>>> 530 gives a 0. (the same should be done to dx).
>>> I still do not understand how does gnuplot handles a one dimensional image.
>>
>> Does this produce an image with the proper height displayed (i.e. the y 
>> extent is from 0.5 to 1.5)?
>>
>> Ben
>>
>
> It was a little tricky cause gnuplot puts the origin in the middle of
> the first pixel, not in the corner.
> I think this patch fixes the issue. Could you verify and if so apply?

gosh, wrong patch. I think this one is correct.

1dimages_gnuplot.diff
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