[Dev-luatex] How to crop bitmap images

Hans Hagen pragma at wxs.nl
Mon Jul 1 15:56:18 CEST 2013


On 7/1/2013 2:59 PM, Patrick Gundlach wrote:
>
> Am 01.07.2013 um 14:32 schrieb Hans Hagen <pragma at wxs.nl>:
>
>> On 7/1/2013 1:51 PM, Patrick Gundlach wrote:
>>> Hi,
>>>
>>> I'd like to crop a bitmap image. How? This is my code for image inclusion:
>>>
>>> -------
>>> \directlua{
>>>    image = img.scan{filename="hacker.jpg"}
>>>    tex.box[0] = node.hpack(img.node(image))
>>> }
>>>
>>> \box0
>>> -------
>>>
>>> bbox{...} seems to work only with PDF images.
>>
>> use the pdf clip operator i.e. set a path with 'l' and 'm' and then apply the operator 'W n'
>
> where?
>
> I mean, what is a good place to put the pdf instructions?

best pack the img in a box and then put some qQ around it with the clip 
at the end (the usual experimenting with origin), so basically something 
compatible to

\pdfliteral {q clip spec}
\pdfximage{...}
\pdfliteral {Q}

ending up in something

q 0 w 0 0 m 29.99991  0 l 29.99991 39.9999 l 0 39.9999 l W n
BT
/F1 11.955168 Tf 1 0 0 1 -10 51.8346 Tm [<00730073>]TJ
ET
Q

this is a clip path: x,y=10bp,20bp w,h=30bp,40bp

(using text XX instead of image)


Hans

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