<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv=Content-Type content="text/html; charset=us-ascii">
<meta name=Generator content="Microsoft Word 12 (filtered medium)">
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:"Lucida Console";
panose-1:2 11 6 9 4 5 4 2 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;}
@page Section1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.Section1
{page:Section1;}
-->
</style>
<!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang=EN-GB link=blue vlink=purple>
<div class=Section1>
<p class=MsoNormal>Hi list,<o:p></o:p></p>
<p class=MsoNormal>I’d posted earlier today to ask about how to copy a
cairo surface into a pre-existing buffer. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I’ve made some progress, as below, but my bitmap is
rendered upside down and back to front. This is to be expected, due to
the <a href="http://en.wikipedia.org/wiki/BMP_file_format">bottom up format of
the Bitmap format</a>.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Flipping every bitmap is expensive, and I’d like to
avoid doing that. My use of cairo is probably incorrect, I think I may need
to use an alternative to creating a DIB etc..<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I’m <a
href="http://msdn.microsoft.com/en-us/library/dd758088(VS.85).aspx">writing a
DirectShow Source Filter</a>, so I can’t use device contexts, I can only render
to a pre-allocated memory block, as acquired from <a
href="http://msdn.microsoft.com/en-us/library/dd407001(VS.85).aspx">IMediaSample</a>.
<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I allocate a cairo surface like this:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal> <span
style='font-size:10.0pt;font-family:"Lucida Console"'>m_pSurface =
cairo_win32_surface_create_with_dib(CAIRO_FORMAT_ARGB32, m_nImageWidth,
m_nImageHeight );</span><o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>And I reuse this each frame.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>At render time, when I’m writing to the supplied
buffer, I do so like this:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console";color:blue'>void</span><span style='font-size:
10.0pt;font-family:"Lucida Console"'> SrcOutPin::DrawFrame( BYTE* pData, LONG
lDataLen )<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'>{ <o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> cairo_surface_t * pSurface =
NULL;<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> <span
style='color:blue'>unsigned</span> <span style='color:blue'>char</span> * pBuffer =
NULL;<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> <span
style='color:blue'>if</span>( m_pSurface && m_pCR )<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> {<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> //<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> <span
style='color:green'>// { cairo specific drawing stuff here }<o:p></o:p></span></span></p>
<p class=MsoNormal style='margin-left:36.0pt;text-indent:36.0pt;text-autospace:
none'><span style='font-size:10.0pt;font-family:"Lucida Console";color:green'>//</span><span
style='font-size:10.0pt;font-family:"Lucida Console"'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> <span
style='color:green'>// Get a byte ptr to the surface data<o:p></o:p></span></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> cairo_surface_t
* pSurface = cairo_win32_surface_get_image( m_pSurface );<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> <span
style='color:blue'>unsigned</span> <span style='color:blue'>char</span> *
pBuffer = cairo_image_surface_get_data(
pSurface );<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> memcpy(
(<span style='color:blue'>void</span>*)pData, (<span style='color:blue'>const</span>
<span style='color:blue'>void</span>*) pBuffer, lDataLen );<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> <o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> m_lFrameCount++;<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> }<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'>}<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Lucida Console"'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Lucida Console"'>While
this memcpy succeeds, the bitmap is upside down and back to front.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Lucida Console"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Lucida Console"'>To
my question:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Lucida Console"'>Windows
has many functions (e.g. <a
href="http://msdn.microsoft.com/en-us/library/ms940373.aspx">StretchBlt</a>) to
solve this problem when working with device contexts, but not when working with
memory buffers (to my knowledge). <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Lucida Console"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Lucida Console"'>Since
I can’t use a device context in this instance, is there another, more
suitable method to use in order to achieve what I need ???<o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>thanks<o:p></o:p></p>
</div>
</body>
</html>