[cairo] offset drawing in a surface

[Bill Spitzak]

swati upadhyaya wrote:
> Hi Henry and Andrea,
> 
> First of all thanks for reply 
>                                  
>                                   I didn't get what you people mentioned 
> as I am new to cairo lib . Let me explain my problem briefly, Suppose I 
> have a device with screen width and height as 400 x 400. And I have an 
> image with 200 x 200. Now in my device for this image start of x=100 and 
> end of x = 300. Now I have to draw the line from 100 to 300..I am using 
> the API
> surface = cairo_image_surface_create_for _data(unsigned char 
> *buff,CAIRO_FORMAT_ARGB32,width,height,cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32,width))
> where width is image width = 200
> height is image height = 200.
> Then I am doing 
> cr = cairo_create(surface);
> 
> Now the problem is as the surface starts from top left only so it will 
> go from 0 to 200 but I want to draw form 100 to 300. So
> 1) what can I do to shift the origin of the surface fom 0 to 100 ? So 
> that it will draw on the same..

You want to do cairo_translate(cr, -100, -100)

Then the point 100,100 will be in the top-left of your image.