[cairo] Get pixeldata from image

[Lobais]

Thanks a lot.
Now I just have to ask how I save the changes? It seems like
cairo_image_surface_get_data only returns a copy of the data.
I've tried to use the create_for_data function to create a new surface from
the data, and save it using write_to_png, but it seems like it creates a few
problems for some pixel, that get totally white..

I'm using pycairo, but guess it should be working the same way:

surface = cairo.ImageSurface.create_from_png(test.png)
buffer = surface.get_data_as_rgba()
surface = cairo.ImageSurface.create_for_data (
            buffer, cairo.FORMAT_ARGB32,
            surface.get_width(), surface.get_height(),
            surface.get_stride())
surface.write_to_png("test_out.png")

On 11/19/06, Andrew McRae <amcrae at employees.org> wrote:
>
> On Sun, 2006-11-19 at 12:57 +0100, Lobais wrote:
> > Hi, it is possible to get the image data of an image, such that one
> > would be able to e.g. get red, green and blue from pixel 8 row 4?
> >
> > --
> > Best Regards, Thomas
>
> The easiest way (from what I know) is to use
> cairo_image_surface_get_data and friends. As long
> as you know it's a RGB or ARGB format (you can check
> with cairo_image_surface_get_format), it's
> going to be a 32 bit pixel element image.
>
> Here's a sample code snippet:
>
>   unsigned char *data = cairo_image_surface_get_data(surface);
>   int stride = cairo_image_surface_get_stride(surface);
>
>   uint32_t *pixelptr;
>   ...
>       pixelptr = (uint32_t *)(data + 4 * stride); // row 4
>       my_pixel = pixel[8];                        // pixel 8
>       red = (pixel[8] >> 16) & 0xFF;
>
> Cheers,
> AMc
>
>


-- 
Mvh. Thomas
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