[cairo] Cairo Drawing Speed
Duong Hoang Linh
linh.duong at quantuminventions.com
Tue Nov 24 01:49:45 PST 2009
I change to use image surface and amazingly drawing time is now only
Thanks for your helps. I think this thread can be closed now.
Duong Hoang Linh wrote:
> Hi Maarten,
> I think i used win32 surface. Below is the code for initializing my
> cairo structure before drawing:
> //Cairo structures
> cairo_surface_t *surface;
> cairo_t *cr;
> int ww, wh;
> RECT rc;
> ww = (rc.right - rc.left);
> wh = (rc.bottom - rc.top);
> HDC memdc;
> HBITMAP hbuffer;
> memdc = CreateCompatibleDC(paintDC.m_hDC);
> hbuffer = CreateCompatibleBitmap(paintDC.m_hDC, ww, wh);
> SelectObject(memdc, hbuffer);
> surface = cairo_win32_surface_create (memdc); // to the memory DC
> cr = cairo_create (surface);
> It may be a good idea to use image surface. I will try out and compare.
> Maarten Bosmans wrote:
>> Your code looks like the right way to construct these lines.
>> What backend are you using? It could very well be that using an
>> imagesurface to draw the lines and then blit the result to the screen
>> is faster.
>> And of course it is always faster if the lines are aligned on the
>> pixel grid, but in your case that's probably not possible because of
>> diagonal line segments.
>> 2009/11/24 Duong Hoang Linh <linh.duong at quantuminventions.com>:
>>> Hi Emmanuel,
>>> This is my code for drawing line:
>>> cairo_set_source_rgb (cr, 0, 0, 0);
>>> cairo_set_line_width (cr, 7);
>>> cairo_set_line_cap (cr, CAIRO_LINE_CAP_ROUND);
>>> cairo_set_line_join (cr, CAIRO_LINE_JOIN_ROUND);
>>> for(int k=0;k<vLines.size();k++)
>>> cairo_move_to (cr, vLines[k].ptLineArray.x, vLines[k].ptLineArray.y);
>>> for(int i=1;i<vLines[k].numLinePoints;i++)
>>> cairo_line_to (cr, vLines[k].ptLineArray[i].x, vLines[k].ptLineArray[i].y);
>>> cairo_stroke_preserve (cr);
>>> cairo_set_source_rgb (cr, 1, 1, 1);
>>> cairo_set_line_width (cr, 4);
>>> cairo_stroke (cr);
>>> I run this code on wince 5.0 device, processor ARM920T, 40MB RAM.
>>> In more detail, i measure the time execution of cairo_stroke and it takes
>>> from 100-120ms. And in total, i need to do cairo_stroke 6 times, which add
>>> up to 700+ms.
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