[cairo] patch [1/1] invert image in _cairo_gl_surrface_map_to_image
Andrea Canciani
ranma42 at gmail.com
Thu Jan 12 23:56:27 PST 2012
On Fri, Jan 13, 2012 at 1:05 AM, Henry (Yu) Song - SISA
<hsong at sisa.samsung.com> wrote:
> Hey, Andrea
>
> I looked at your negative stride image code,
> The effect of calling cairo_image_surface_create_for_data (data + stride * (height - 1), format, width, height, -stride) is same as calling
> _cairo_image_surface_create_with_pixman_format (data, format, width, height, -1), the stride parameter is tested and ignored in cairo-image-surface.c
No, it's not ignored, it's respected.
This means that the "data" buffer will contain the image in bottom to
top order and that cairo-image will use it in the same order, too.
>
> I don't see invert image comes out.
If you want to see an inverted image coming out, you should
"misinterpret" the buffer, as in the attachment
(data is filled drawing to png_image, which is top to bottom, then
read through inv, which is bottom to top)
IIRC GL gives you a buffer in a bottom to top order, hence you simply
need to wrap it into a top to bottom (aka negative stride) image.
No additional cairo-image allocation nor temporary buffers ;)
Andrea
>
> Thanks
>
> Henry
>
>
> -----Original Message-----
> From: cairo-bounces+hsong=sisa.samsung.com at cairographics.org [mailto:cairo-bounces+hsong=sisa.samsung.com at cairographics.org] On Behalf Of Andrea Canciani
> Sent: Wednesday, January 04, 2012 11:08 AM
> To: Henry Song
> Cc: cairo at cairographics.org
> Subject: Re: [cairo] patch [1/1] invert image in _cairo_gl_surrface_map_to_image
>
> On Wed, Jan 4, 2012 at 4:57 PM, Henry Song <henry.song at samsung.com> wrote:
>> Hi, Andrea
>>
>> The patch creates a dst of inv_image and the source is image, they are not
>> same, aren't they?
>
> Sorry, you're right, I misread the pattern creation.
> Andrea
>
>>
>> Thanks
>>
>> Henry
>>
>> -----Original Message-----
>> From: cairo-bounces+henry.song=samsung.com at cairographics.org
>> [mailto:cairo-bounces+henry.song=samsung.com at cairographics.org] On Behalf Of
>> Andrea Canciani
>> Sent: Wednesday, January 04, 2012 12:43 AM
>> To: Henry (Yu) Song - SISA
>> Cc: cairo at cairographics.org
>> Subject: Re: [cairo] patch [1/1] invert image in
>> _cairo_gl_surrface_map_to_image
>>
>> On Wed, Jan 4, 2012 at 1:56 AM, Henry (Yu) Song - SISA
>> <hsong at sisa.samsung.com> wrote:
>>> Date: Fri Dec 30 11:24:54 2011 -0800
>>>
>>> gl: Add support to invert non texture gl surface image that does not
>> have
>>> GL_MESA_pack_invert when map from gl surface to image surface
>>>
>>> diff --git a/src/cairo-gl-surface.c b/src/cairo-gl-surface.c
>>> index 8f69033..8b8f196 100644
>>>
>>> --- a/src/cairo-gl-surface.c
>>> +++ b/src/cairo-gl-surface.c
>>> @@ -1001,6 +1001,10 @@ _cairo_gl_surface_map_to_image (void
>> *abstract_surface,
>>> unsigned int cpp;
>>> cairo_bool_t invert;
>>> cairo_status_t status;
>>> + cairo_t *inv_cr = NULL;
>>> + cairo_image_surface_t *inv_image = NULL;
>>> + cairo_pattern_t *inv_pattern = NULL;
>>> + cairo_matrix_t inv_matrix;
>>>
>>> /* Want to use a switch statement here but the compiler gets whiny. */
>>> if (surface->base.content == CAIRO_CONTENT_COLOR_ALPHA) {
>>> @@ -1093,6 +1097,50 @@ _cairo_gl_surface_map_to_image (void
>> *abstract_surface,
>>> image = (cairo_image_surface_t *)
>>> _cairo_surface_create_in_error (status);
>>> }
>>> +
>>> + /*
>>> + * FIXME: we must invert the image if it is non texture surface,
>>> + * and it does not have GL_MESA_pack_invert.
>>> + * Is there more efficient way to invert image?
>>
>> Using negative stride might be more efficient, but some backends might
>> not (yet) support them correctly.
>>
>> Side note:
>> It is already possible to create negative stride images.
>> Should we add a test trying to use them and support them?
>> Unless I get feedback, I'll try to write the test this weekend.
>>
>>> + */
>>> +
>>> + if (! _cairo_gl_surface_is_texture (surface) && ! invert) {
>>> + inv_image = (cairo_image_surface_t*)
>>> + _cairo_image_surface_create_with_pixman_format (NULL,
>>> + pixman_format,
>>> + extents->width,
>>> + extents->height,
>>> + -1);
>>> + if (unlikely (inv_image->base.status)) {
>>> + goto CLEAR_IMAGE;
>>> + }
>>> +
>>> + image->base.is_clear = FALSE;
>>> + inv_pattern = cairo_pattern_create_for_surface (&image->base);
>>> + if (unlikely (inv_pattern->status)) {
>>> + goto CLEAR_PATTERN;
>>> + }
>>> + cairo_matrix_init_scale (&inv_matrix, 1.0, -1.0);
>>> + cairo_matrix_translate (&inv_matrix, 0, -(extents->height));
>>> + cairo_pattern_set_matrix (inv_pattern, &inv_matrix);
>>> +
>>> + inv_cr = cairo_create (&inv_image->base);
>>> + if (unlikely (inv_cr->status)) {
>>> + goto CLEAR_CAIRO;
>>> + }
>>> + cairo_set_source (inv_cr, inv_pattern);
>>> + cairo_set_operator (inv_cr, CAIRO_OPERATOR_SOURCE);
>>> + cairo_paint (inv_cr);
>>
>> You're using the same surface as source and as destination.
>> This results in undefined behavior.
>> If you want to flip the image like this, you should use two independent
>> surfaces
>>
>>
>>> + cairo_surface_destroy (&image->base);
>>> + image = (cairo_image_surface_t *)cairo_surface_reference
>> (&inv_image->base);
>>> + }
>>> +
>>> +CLEAR_CAIRO:
>>> + cairo_destroy (inv_cr);
>>> +CLEAR_PATTERN:
>>> + cairo_pattern_destroy (inv_pattern);
>>> +CLEAR_IMAGE:
>>> + cairo_surface_destroy (&inv_image->base);
>>>
>>> return &image->base;
>>> }
>>> --
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