[cairo] (no subject)

[Petr Kobalíček]

I would also refer to any html5 canvas tutorial in this case, I think there
is no real difference between cairo gradients and <canvas> gradients.

On Fri, Jul 10, 2015 at 6:54 PM, Andrea Canciani <ranma42 at gmail.com> wrote:

> On Fri, Jul 10, 2015 at 4:21 PM, Roman Goldov <goldov1 at yandex.ru> wrote:
>
>> I am a new user of GTK+ and of Cairo. That is why I would appreciate
>> detailed answers for my questions.
>>
>> From the manual:
>> "cairo_pattern_create_linear(x0,y0,x1,y1) -  Before using the gradient
>> pattern, a number of color stops should be defined using
>> cairo_pattern_add_color_stop_rgb() or cairo_pattern_add_color_stop_rgba()."
>>
>> do i understand corerectly that this function is a general function -
>> that is it says only to create a linear gradient
>> between (x0,y0) and (x1,y1) points, and the colors are defined by, for
>> example, cairo_pattern_add_color_stop_rgb()
>> function ?
>>
>
> Yes, the cairo_pattern_create_linear() function creates a pattern whose
> colors are chosen calling cairo_pattern_add_color_stop_rgb[a]().
> The linear gradient is obtained by projecting all of the points of the
> plane (or, equivalently, by looking for the nearest point) to the
> (infinite) line passing through (x0,y0) and (x1,y1). Each of these point is
> associated with a parameter which varies from 0 to 1 along the segment that
> defines the line.
> The color stops define the color in the [0,1] range.
> For values outside of the [0,1] range, a extend mode is applied
> http://cairographics.org/manual/cairo-cairo-pattern-t.html#cairo-extend-t.
>
>
>>
>> cairo_pattern_add_color_stop_rgb (cairo_pattern_t *pattern, double
>> offset, double red, double green, double blue) -
>> whst does "offset" mean in terms of the colors? is it a number ? in which
>> range it is varied ?
>>
>
> The extremes (x0,y0) and (x1,y1) are respectively at offset 0 and 1.
>
> I hope this helps you (we should definitely improve the documentation,
> suggestions and patches are welcome ;) ).
>
> Andrea
>
>
>>
>> Thank you.
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>> cairo at cairographics.org
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>
>
>
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