[NTG-context] error when using externalfigure

Sietse Brouwer sbbrouwer at gmail.com
Mon Nov 26 16:01:51 CET 2012


This seems to me a case of garbage in, garbage out; I'd say it's the
script's job, rather than ConTeXt's, to ensure the images have the
correct dpi to get a reasonable width in inches. (Brr. I hate inches.
Disgusting, Mars-mission-wrecking way of measuring things.)

Here is some pseudocode. You'd still need a way to get
image.width_in_pixels and image.dpi from the image; I daresay either
`convert` or `exiftool` can do the job. See also this recent mail to
the list by Guy Stalnaker:
http://archive.contextgarden.net/message/20121123.232556.bf205641.en.html

projected_width = image.width_in_pixels / image.dpi
if projected_width > max_width_in_inches then
   required_dpi = image.width_in_pixels / max_width_in_inches
   shell('convert --density %f %s', required_dpi, image_name)
end

Cheers,
Sietse

On Mon, Nov 26, 2012 at 1:32 PM, Hans Hagen <pragma at wxs.nl> wrote:
> On 11/26/2012 11:00 AM, luigi scarso wrote:
>>
>> On Mon, Nov 26, 2012 at 10:50 AM, Hans Hagen <pragma at wxs.nl> wrote:
>>>
>>> On 11/26/2012 10:36 AM, luigi scarso wrote:
>>>>
>>>>
>>>> On Mon, Nov 26, 2012 at 10:20 AM, Pavel Dohnal <pavel.dohnal at twobits.cz>
>>>> wrote:
>>>>>
>>>>>
>>>>> Hello,
>>>>> I have a big context source file which contains pictures from different
>>>>> sources. The problem is, that there are some pictures the context
>>>>> cannot
>>>>> process. It displays an error message and ends. I run the context from
>>>>> another script in batchmode. After finishing, the context creates a PDF
>>>>> file, which contains this problematic picture but the pdf is broken. It
>>>>> does
>>>>> not have numbers in the table of contents and it is not arranged by
>>>>> setup.
>>>>> Here is a minimal example:
>>>>> \starttext
>>>>>
>>>>>
>>>>> \externalfigure[http://cdn-locations-images.tripomatic.com/img-poi1295-5ZTynx-s.jpg][width=26.5mm]
>>>>> \stoptext
>>>>
>>>>
>>>>
>>>>
>>>> when I save the jpg  as eps from gimp
>>>> I see
>>>> width = 6096,00
>>>> height=4064,00
>>>>
>>>> The first value is off for TeX.
>>>
>>>
>>>
>>> if i print the values from the img object i get
>>>
>>> 17344.8pt
>>> 11563.2pt
>>>
>>> so the problem is deep down in the jpg reader ... the image is crippled
>>> in
>>> the sense that it has no valid resolution information
>>>
>>> something for hartmut to check in the img lib
>>
>>
>> Hm, I'm not sure. It's an image that could be correct, but TeX cannot
>> manage it.
>> It has 240x160 pixels and 1ppi, so it's 6,096 meters x 4,06400meters
>> and 6 meters are too much for TeX (which still has its limits around
>> 5meters)
>> It's ok to print poster maybe, but then  TeX  is not the right tool.
>
>
> yes, but the 1,1 resolution prevents us from doing anything useful, i.e. we
> could for instance have something
>
> if xresolution < 72 then xresolution = 72 end
>
> but I'm not sure what the pdf backend will do as then the uses resolution
> for front and backend differ too much
>
> i'll add an overflow check but keep in mind that in that case scaling is
> bases on the limited size
>
>
> -----------------------------------------------------------------
>                                           Hans Hagen | PRAGMA ADE
>               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
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>                                              | www.pragma-pod.nl
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