Re: [gthumb-list] Writing an extension - how to overlay metadata on images?

[Paolo Bacchilega <paolo bacchilega libero it>]

Il 01/03/19 19:11, Phil Ashby ha scritto:
> Hi gThumb list,

Hello,

> My question for the list:
>
> How /should/ I go about overlaying metadata on loaded images? Where and 
> how should I intercept the rendering process (it feels like there should 
> be hooks registered but I cannot find any)?

A possible way is to use the gth-browser-activate-viewer-page hook, 
inside the hook function you have to check if the current viewer page is 
of type GTH_IMAGE_VIEWER_PAGE, as an example see the function 
ir__gth_browser_activate_viewer_page_cb in 
extensions/image_rotation/callbacks.c.

If it's a GTH_IMAGE_VIEWER_PAGE, you can use 
gth_image_viewer_page_get_image_viewer to get the image viewer widget 
and then use gth_image_viewer_add_painter to add a function that will 
used to paint something over the image, as an example see the 
paint_comment_over_image_func in 
extensions/image_viewer/gth-image-viewer-page.c.

A painter function gets a cairo context, so from there you can just use 
cairo to paint over the image.

- Paolo