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<p class=MsoNormal>Hi list,<o:p></o:p></p>
<p class=MsoNormal>I’m writing a source filter for <a
href="http://en.wikipedia.org/wiki/DirectShow">DirectShow</a> <span
style='color:#1F497D'>on the win32 platform </span>and I’m hoping to use Cairo
to generate simple overlay graphics for a video feed.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The source filter generates media frames (bitmaps).
For each frame, I have the following code:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>// I have the following member variables created:<o:p></o:p></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'>cairo_surface_t * m_pSurface;<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Lucida Console"'>cairo_t
* m_pCR;<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>// and I create the surface like
so:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Lucida Console"'>m_pSurface
= cairo_win32_surface_create_with_dib( cairoFmt, m_nImageWidth, m_nImageHeight
);</span><span style='color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>// the drawing function<o:p></o:p></span></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"'> <span
style='color:blue'>char</span>
szTime [50];<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'>
SYSTEMTIME
tmCurrentTime; <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"'>
GetLocalTime(&tmCurrentTime);<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'>// clear the surface to transparent
<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_save(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"'>
cairo_set_operator( m_pCR, CAIRO_OPERATOR_CLEAR );<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'>
cairo_paint(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"'>
cairo_restore(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"'> <span
style='color:green'>// write the time <o:p></o:p></span></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> _snprintf( <o:p></o:p></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"'>szTime, <o:p></o:p></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"'>50, <o:p></o:p></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:#A31515'>"%.2d:%.2d:%.2d\0"</span><span
style='font-size:10.0pt;font-family:"Lucida Console"'>, <o:p></o:p></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"'>tmCurrentTime.wHour,
<o:p></o:p></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"'>tmCurrentTime.wMinute,
<o:p></o:p></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"'>tmCurrentTime.wSecond
<o:p></o:p></span></p>
<p class=MsoNormal style='text-indent:36.0pt;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"'>
cairo_set_source_rgba( m_pCR, 0.0, 0.0, 0.0, 1.0 );<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'>
cairo_select_font_face ( m_pCR, <span style='color:#A31515'>"Sans"</span>,
CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_BOLD );<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'>
cairo_set_font_size ( m_pCR, 14.0 );<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> cairo_move_to (
m_pCR, 40.0, 40.0 );<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console"'> cairo_show_text (
m_pCR, szTime );<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_paint(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"'> <span
style='color:green'>// TODO: copy the cairo surface data into the sample buffer<o:p></o:p></span></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Lucida Console";color:green'> // I
imagine this might be a memcpy() call from source to pData<o:p></o:p></span></p>
<p class=MsoNormal style='text-indent:36.0pt;text-autospace:none'><span
style='font-size:10.0pt;font-family:"Lucida Console"'>memcpy((void*)pData,
(void*)???, lDataLen);<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"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Lucida Console"'>I’d
seen <a href="http://www.cairographics.org/FAQ/#paint_from_a_surface">the
section in the FAQ</a> on painting from one surface to another, but I’m just
guessing and I’m not sure that this would be suitable. Can someone show
me the correct procedure?<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"'>thanks,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Lucida Console"'>john</span><o:p></o:p></p>
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