Re: image-size

[Willem Rein Oudshoorn]

Eli Zaretskii <address@hidden> writes:

>> From: Lars Magne Ingebrigtsen <address@hidden>
>> Date: Thu, 20 Jun 2013 22:57:10 +0200
>> Cc: address@hidden
>> 
>> As Chong said:
>> 
>> > You have to replace the call to lookup_image in `image-size' with a
>> > new function that avoids loading the image.
>
> What do you mean by "loading the image"?  You cannot have the size
> without reading the image file.

Well, I do not know for jpeg etc. But the png file format has the image
size in pixels right at the start of the file, so you only need to read
in a tiny part of the file.

For png the width is big-endian integer starting at byte 16, and
the height starts at 20.

Wim Oudshoorn.