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<p>Sorry, by i already have the BlendFunc method.</p>
<p>I initialize my opengl system with this code:</p>
<p>glViewport(0, 0, drm->rect()->w, drm->rect()->h);<br>
glDisable(GL_CULL_FACE);<br>
glEnable(GL_LESS);<br>
glEnable(GL_BLEND);<br>
glEnable(GL_TEXTURE_2D);<br>
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);</p>
<p><br>
</p>
<p>Lorenzo.<br>
</p>
<br>
<div class="moz-cite-prefix">On 08/08/2018 08:00 PM, Bill Spitzak
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAL-8oAggRSucr6krBQnLE7g4ZUe3aisdu7HwZW3M1-Fk1G5h1g@mail.gmail.com">
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<div>glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);</div>
<div><br>
</div>
<div>Sorry, I managed to cut & paste the one example I had
that did not say "ALPHA"</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Wed, Aug 8, 2018 at 10:59 AM, Bill
Spitzak <span dir="ltr"><<a
href="mailto:spitzak@gmail.com" target="_blank"
moz-do-not-send="true">spitzak@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">You have to change the OpenGL compositing to
over the premultiplied image. I think glBlendFunc(GL_ONE,
GL_ONE_MINUS_SRC_COLOR) is what you need.</div>
<div class="HOEnZb">
<div class="h5">
<div class="gmail_extra"><br>
<div class="gmail_quote">On Wed, Aug 8, 2018 at 8:16
AM, Lorenzo <span dir="ltr"><<a
href="mailto:gatti88@libero.it" target="_blank"
moz-do-not-send="true">gatti88@libero.it</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<br>
<br>
i have a problem with the creation of a rounded
rectangle with cairo.<br>
<br>
Environment info:<br>
<br>
cairo version: 1.14.8-1<br>
<br>
OS: linux<br>
<br>
<br>
A linux client creates a rounded rectangle with
the following code:<br>
<br>
let x = 0.0<br>
let y = 0.0<br>
let w = Double(size.w)<br>
let h = Double(size.h)<br>
let r = 20.0<br>
<br>
logger.verbose("rounded rectangle
x=\(x),y=\(y),w=\(w),h=\(h),r=<wbr>\(r)")<br>
<br>
cairo_move_to(context, x, y + r)<br>
cairo_arc(context, x + r, y + r, r,
Double.pi, -Double.pi / 2.0)<br>
cairo_line_to(context, x + w - r, y)<br>
cairo_arc(context, x + w - r, y + r, r,
-Double.pi / 2.0, 0.0)<br>
cairo_line_to(context, x + w, y + h - r)<br>
cairo_arc(context, x + w - r, y + h - r,
r, 0.0, Double.pi / 2.0)<br>
cairo_line_to(context, x + r, y + h)<br>
cairo_arc(context, x + r, y + h - r, r,
Double.pi / 2.0, Double.pi)<br>
cairo_close_path(context)<br>
<br>
<br>
cairo_set_source_rgba(context, cl.red,
cl.green, cl.blue, cl.alpha);<br>
cairo_fill(context)<br>
<br>
<br>
After the surface fill i have 2 different
operations to be performed:<br>
<br>
- write the png on the disk using
"cairo_surface_write_to_png(su<wbr>rface,
"testcairo.png")"<br>
<br>
- display the png with opengl es 3.0 as a
texture (done by copy the surface raw bytes with
cairo_image_surface_get_data(s<wbr>urface)<br>
<br>
in a shared memory used by the opengl server
program)<br>
<br>
<br>
Save the image on disk is ok, the image is good.<br>
<br>
Display the image as a texture with opengl results
in an ugly image: corners have some black pixels
around them.<br>
<br>
Why this difference?<br>
<br>
<br>
I have done some checks:<br>
<br>
- data obtained with cairo_image_surface_get_data
are the same that the graphics server loads from
the shared memory (checked PixelxPixel) so the
data transfer don't is the problem (checked also
any signed/unsigned byte conversion)<br>
<br>
- loading the disk png as a texture instead of
loading data from the shared memory results in a
good image with no problems.<br>
<br>
<br>
My opinion is that the cairo_surface_write_to_png
performs an antialiasing algorithm and accessing
raw data bypass it taking the original image.<br>
<br>
<br>
Is my opinion correct? If yes, any advice to solve
the problem?<br>
<br>
<br>
Regards,<br>
<br>
Lorenzo.<span class="m_-5063440743205944044HOEnZb"><font
color="#888888"><br>
<br>
<br>
<br>
<br>
<br>
-- <br>
cairo mailing list<br>
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target="_blank" moz-do-not-send="true">cairo@cairographics.org</a><br>
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href="https://lists.cairographics.org/mailman/listinfo/cairo"
rel="noreferrer" target="_blank"
moz-do-not-send="true">https://lists.cairographics.or<wbr>g/mailman/listinfo/cairo</a></font></span></blockquote>
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