RE: [Vxl-users] [patch] add RGBA support for saving PNG files

[Wheeler, F. W (Research) <wh...@cr...>]

Petr,

I get this error with your patch.

Building object file vil_png.obj...
vil_png.cxx
C:\cygwin\home\200006507\dev\vxl_src\core\vil\file_formats\vil_png.cxx(382)
: error C2065: 'PNG_COLOR_TYPE_RGBA' : undeclared identifier

All my builds use the png from vxl/v3p/png/.  According to vxl/v3p/png.URL,
that is derived from this version,

ftp://ftp.uu.net/graphics/png/src/libpng-1.0.8.tar.gz

I see PNG_COLOR_TYPE_RGB_ALPHA defined in there.  I assume you are using
some different version of png.  Can you make your patch accommodate both?
Perhaps a few ifdefs will do it.

Fred Wheeler


> -----Original Message-----
> From: Petr Konecny [mailto:pe...@am...]
> Sent: Tuesday, January 13, 2004 3:28 PM
> To: vxl...@li...
> Subject: [Vxl-users] [patch] add RGBA support for saving PNG files
> 
> 
> Hi,
> 
> the following adds support for saving alpha channel into RGB PNG
> files. Tested both for 8 and 16 bits/channel.
> 
> I use test nplanes()==4 as an indication of RGBA file. IMHO 
> this should
> not break existing code, because the original version halts on assert
> when nplanes()==4.
> 
> PNG supports alpha also for grayscale images, however I did not
> implement it.
> 
>                                               Thanks, Petr
> 
> Index: core/vil/file_formats/vil_png.cxx
> ===================================================================
> RCS file: /cvsroot/vxl/vxl/core/vil/file_formats/vil_png.cxx,v
> retrieving revision 1.16
> diff -u -r1.16 vil_png.cxx
> --- core/vil/file_formats/vil_png.cxx	9 Dec 2003 14:58:16 
> -0000	1.16
> +++ core/vil/file_formats/vil_png.cxx	13 Jan 2004 20:21:03 -0000
> @@ -378,7 +378,9 @@
>    png_set_write_fn(p_->png_ptr, vs_, user_write_data, 
> user_flush_data);
>  
>    int color_type;
> -  if (components_ == 3)
> +  if (components_ == 4)
> +    color_type = PNG_COLOR_TYPE_RGBA;
> +  else if (components_ == 3)
>      color_type = PNG_COLOR_TYPE_RGB;
>    else
>      color_type = PNG_COLOR_TYPE_GRAY;
> @@ -488,9 +490,8 @@
>          for (unsigned x=0; x < view.ni(); ++x)
>            rows[y0+y][x0+x] = view2(x,y);
>      }
> -    else
> +    else if (nplanes()==3)
>      {
> -      assert(nplanes() == 3);
>        for (unsigned y = 0; y < view.nj(); ++y)
>          for (unsigned x=0; x < view.ni(); ++x)
>          {
> @@ -499,6 +500,18 @@
>            rows[y0+y][(x0+x)*3+2] = view2(x,y,2);
>          }
>      }
> +    else
> +    {
> +      assert(nplanes() == 4);
> +      for (unsigned y = 0; y < view.nj(); ++y)
> +        for (unsigned x=0; x < view.ni(); ++x)
> +        {
> +          rows[y0+y][(x0+x)*4] = view2(x,y,0);
> +          rows[y0+y][(x0+x)*4+1] = view2(x,y,1);
> +          rows[y0+y][(x0+x)*4+2] = view2(x,y,2);
> +          rows[y0+y][(x0+x)*4+3] = view2(x,y,3);
> +        }
> +    }
>    }
>    else if (bits_per_component_ == 16)
>    {
> @@ -510,15 +523,26 @@
>          for (unsigned x=0; x < view.ni(); ++x)
>            
> *reinterpret_cast<vxl_uint_16*>(&rows[y0+y][(x0+x)*2]) = view2(x,y);
>      }
> -    else
> +    else if (nplanes() == 3)
>      {
> -      assert(nplanes() == 3);
>        for (unsigned y = 0; y < view.nj(); ++y)
>          for (unsigned x=0; x < view.ni(); ++x)
>          {
>            
> *reinterpret_cast<vxl_uint_16*>(&rows[y0+y][(x0+x)*6]) = view2(x,y,0);
>            
> *reinterpret_cast<vxl_uint_16*>(&rows[y0+y][(x0+x)*6+2]) = 
> view2(x,y,1);
>            
> *reinterpret_cast<vxl_uint_16*>(&rows[y0+y][(x0+x)*6+4]) = 
> view2(x,y,2);
> +        }
> +    }
> +    else 
> +    {
> +      assert(nplanes() == 4);
> +      for (unsigned y = 0; y < view.nj(); ++y)
> +        for (unsigned x=0; x < view.ni(); ++x)
> +        {
> +          
> *reinterpret_cast<vxl_uint_16*>(&rows[y0+y][(x0+x)*8]) = view2(x,y,0);
> +          
> *reinterpret_cast<vxl_uint_16*>(&rows[y0+y][(x0+x)*8+2]) = 
> view2(x,y,1);
> +          
> *reinterpret_cast<vxl_uint_16*>(&rows[y0+y][(x0+x)*8+4]) = 
> view2(x,y,2);
> +          
> *reinterpret_cast<vxl_uint_16*>(&rows[y0+y][(x0+x)*8+6]) = 
> view2(x,y,3);
>          }
>      }
>    }
> 
> 
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