[cairo] Copying from one surface to another

[Richenderfer, Tom]

Hello,

 

                I am new to using Cairo and I am having a problem
getting my code to work correctly.  I have a set of PNG files that I
want Cairo to read in and copy to a PS surface (doing a PNG -> PS
conversion).  The code seems to work except that all of the PS pages in
the resulting PS file are blank.  I am following the example given in
the Cairo FAQ about copying surfaces.  Any ideas on what I am doing
wrong?  The basic code is:

 

                // create Cairo PS surface

                psSurface =
cairo_ps_surface_create("/var/tmp/PNG2PSPlugin.ps", 864, 1584);

                if(cairo_surface_status(psSurface) !=
CAIRO_STATUS_SUCCESS)

                {

                                return(false);

                }

 

                // create context

                psTarget = cairo_create(psSurface);

                if(cairo_status(psTarget) != CAIRO_STATUS_SUCCESS)

                {

                                // could not create context, abort

                                return(false);

 

                }

 

                // loop to read the page png files into a PNG surface
and paint into a PS surface

                for(pageNum = 1; ; pageNum++)

                {

                                // build the file name

                                sprintf(pageFileName,
"/var/tmp/PNGFile%d.png", pageNum);

 

                               // try to open the file

                              dataFileHandle.open(pageFileName, ios::in
| ios::binary);

                              if(!dataFileHandle.is_open())

                              {

                                          // at end of file set

                                          break;

                              }

                              else

                              {

                                          dataFileHandle.close();

                              }

 

                                // create the png surface with the file

                                pngSurface =
cairo_image_surface_create_from_png((const char*)pageFileName);

                                if(cairo_surface_status(pngSurface) !=
CAIRO_STATUS_SUCCESS)

                                {

                                                // could not create png
surface, abort

                                                return(false);

                                }

 

                                // paint the png surface to the ps
surface

                                cairo_set_source_surface(psTarget,
pngSurface, 0.0, 0.0);

                                cairo_paint(psTarget);

                                cairo_surface_show_page(psSurface);

                                cairo_surface_destroy(pngSurface);

                }

 

 

                // check on the context

                if(cairo_status(psTarget) != CAIRO_STATUS_SUCCESS)

                {

                                // something went wrong, abort

                                return(false);

                }

 

                // delete the context

                cairo_destroy(psTarget);

 

                // close out drawing to the ps surface

                cairo_surface_finish(psSurface);

 

                // check the status of the ps surface

                if(cairo_surface_status(psSurface) !=
CAIRO_STATUS_SUCCESS)

                {

                                // something went wrong, abort

                                return(false);

                }

 

                // done with the ps surface

                cairo_surface_destroy(psSurface);

 

Thanks,

 

Tom R.

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