[cairo] scaling an image

[Uli Schlachter]

Hi,

On 11.08.2017 22:43, folkert wrote:
> I would like to scale an image.
> Is that something I could do with cairo? Because according to google
> cairo_scale does not resize the surface.

What kind of scaling exactly? The following (untested) code scales an
image to half the size (rounded down); does that help you?

cairo_surface_t *scale_to_half(cairo_surface_t *s, int orig_width, int
orig_height)
{
    cairo_surface_t *result = cairo_surface_create_similar(s,
            cairo_surface_get_content(s), orig_width/2, orig_height/2);
    cairo_t *cr = cairo_create(result);
    cairo_scale(cr, 0.5, 0.5);
    cairo_set_source_surface(cr, s, 0, 0);
    cairo_set_operator(cr, CAIRO_OPERATOR_SOURCE);
    cairo_paint(cr);
    cairo_destroy(cr);
    return result;
}

Cheers,
Uli
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