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One problem is, that tolua/lua does not handle plain data pointers
properly. Therefore something like
local surface = cairo_image_surface_create_for_data(
imlib_image_get_data_for_reading_only(), ..
will fail using the lua bindings. Hence this wrapper, which adds
a function which be used to draw an imlib image to a cairo surface.
This also addresses another issue, drawing images with a transparent
background (e.g. gifs or pngs) to the cairo surface properly. Apparently
the image format of imlib is incompatible to cairos which uses
pre-multiplied data. This is also explained in the cairo documentation.
A fix for this issue is to blend the image with another alpha mask to
get the correct values. The code and explanation for this was taken from
http://lists.cairographics.org/archives/cairo/2008-March/013492.html
Executive Summary: This wrapper function can load (transparent) images
(e.g. gif or png) from a file by using imlib and draw them on a cairo
surface.
6 lines
212 B
Plaintext
6 lines
212 B
Plaintext
$#include <cairo.h>
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$#include <libcairo_imlib2_helper.h>
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void cairo_draw_image(const char *, cairo_surface_t *, int, int, double, double,
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double * return_scale_w, double * return_scale_h);
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