Re: patch [1/1] invert image in _cairo_gl_surrface_map_to_image

On Fri, Jan 13, 2012 at 1:05 AM, Henry (Yu) Song - SISA
<[email protected]> 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: [email protected] [mailto:[email protected]] On Behalf Of Andrea Canciani
> Sent: Wednesday, January 04, 2012 11:08 AM
> To: Henry Song
> Cc: [email protected]
> 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 <[email protected]> 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: [email protected]
>> [mailto:[email protected]] On Behalf Of
>> Andrea Canciani
>> Sent: Wednesday, January 04, 2012 12:43 AM
>> To: Henry (Yu) Song - SISA
>> Cc: [email protected]
>> 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
>> <[email protected]> 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;
>>>  }
>>> --
>>> cairo mailing list
>>> [email protected]
>>> http://lists.cairographics.org/mailman/listinfo/cairo
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/*
 * Copyright 2012 Andrea Canciani
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy,
 * modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * Author: Andrea Canciani <[email protected]>
 */

#include "cairo-test.h"

static const char *png_filename = "romedalen.png";

static cairo_test_status_t
draw (cairo_t *cr, int width, int height)
{
    const cairo_test_context_t *ctx = cairo_test_get_context (cr);
    cairo_format_t format = CAIRO_FORMAT_ARGB32;
    cairo_t *cr_pngimage;
    cairo_surface_t *png, *pngimage, *inv;
    uint8_t *data;
    int stride;

    png = cairo_test_create_surface_from_png (ctx, png_filename);

    stride = cairo_format_stride_for_width (format, width);
    data = calloc (stride, height);
    pngimage = cairo_image_surface_create_for_data (data, format,
						    width, height, stride);
    inv = cairo_image_surface_create_for_data (data + stride * (height - 1),
					       format, width, height, -stride);

    cr_pngimage = cairo_create (pngimage);
    cairo_set_source_surface (cr_pngimage, png, 0, 0);
    cairo_paint (cr_pngimage);
    cairo_destroy (cr_pngimage);

    cairo_set_source_surface (cr, inv, 0, 0);
    cairo_paint (cr);

    cairo_surface_destroy (png);

    cairo_surface_finish (inv);
    cairo_surface_destroy (inv);

    cairo_surface_finish (pngimage);
    cairo_surface_destroy (pngimage);

    free (data);

    return CAIRO_TEST_SUCCESS;
}

CAIRO_TEST (negative_stride_image,
	    "Test that images with a negative stride are handled correctly.",
	    "stride, image", /* keywords */
	    NULL, /* requirements */
	    256, 192,
	    NULL, draw)