[Dev-luatex] How to crop bitmap images

[Hans Hagen]

On 7/1/2013 9:10 PM, Patrick Gundlach wrote:
> Hello Hans,
>
>
>> 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
>
> that works fine, thank you very much! This is my test code now:
>
> -----------------------
> \directlua{
>    a=node.new("whatsit","pdf_literal")
>    b=node.new("whatsit","pdf_literal")
>    a.data = "q 0 w 20 20 m 140  20 l 140 160 l 20 160 l W n "
>    b.data = "Q"
>    image = img.scan{filename="cow.pdf"}
>    i = img.node(image)
>    node.insert_after(a,a,i)
>    node.insert_after(a,i,b)
>    head = node.hpack(a)
>    tex.box[0] = head
> }
>
>
> \box0
>
> \bye

looks ok to me

> -----------------------
>
> I wonder how it compares to the slightly different approach pdflatex uses (pdftex.def?). If I see it correctly the graphicx package creates an xobject/form from the bitmap and changes the bounding box there.

i don't know (never looked into it) but maybe it's wrapped twice then, 
once as image (form) and as box (form) or maybe they add a crop box in 
the resources that then overloads the mediabox

but i guess that the clip is okay (i used that method for years)

Hans


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