Re: Problem Building Ada Interface To ImageMagick 7

[Stephen Leake <stephen_leake@stephe-leake.org>]

On Tuesday, June 26, 2018 at 8:13:03 AM UTC-5, Roger wrote:
> On Tuesday, June 26, 2018 at 7:34:57 PM UTC+10, gautier...@hotmail.com wrote:
> > Is there something specific you want to do with ImageMagick ?
> 
> The current specific thing I'm trying to do (in support of a larger project) is to get ImageMagick to read an image file and writing the image to another file.

One way to do this is to use gnat.os_lib spawn, and run the imagemagick executable. For example, I have this:

   procedure To_Jpeg (I : in Cursor)
   is
      use GNAT.OS_Lib;
      Filename     : constant String  := Element (I);
      Ext_First    : constant Integer := Filename'Last - 3;
      Jpg_Filename : constant String  := Filename (Filename'First .. Ext_First - 1) & ".jpg";
      Success      : Boolean;
   begin
      --  Calling 64 bit cygwin 'convert' from 32 bit native GNAT
      --  screws up, so we use a 32 bit native install of ImageMagick.
      Spawn ("d:/Apps/ImageMagick-7.0.3-Q8/magick.exe",
             (new String'("convert"),
              new String'(Filename),
              new String'("-quality"),
              new String'("50"), -- good for fine text, reasonably small
              new String'(Jpg_Filename)), Success);

      if not Success then
         raise Ada.Text_IO.Use_Error with "convert failed";
      end if;

      File_Names.Replace_Element (I, Jpg_Filename);
   end To_Jpeg;