Re: displaying a very large image

[John Cupitt <jcupitt gmail com>]

On 6/23/05, Cheok Yan Cheng <yccheok yahoo com> wrote:
> currently I plan to work on an application which can
> open a VERY large image (>80 MEG) in a very fast
> manner. there is no delay while user trying to scroll
> along the image. currently, when i open an large image
> with GIMP, i can feel the loading and scrolling delay.
> 
> i was wondering which GTK+ module i should
> start looking at?

I maintain a program which can display very large images (>10 GBytes) with gtk:

  http://www.vips.ecs.soton.ac.uk/

I do image display with a GtkDrawingArea inside a GtkScrolledWindow.
In the expose handler I generate the part of the image which has been
exposed and paint it to the screen with gdk_draw_rgb_image().

There are some complications: If you need to draw geometry over the
top of the image, you need to do translation and clipping yourself if
the lines are going to go over 16 bits in any direction. Also, very
large scrolled windows do not currently work well with the win32
backend (I think a fix is coming soon for this).

John