[AGG] Beginner - how to put an image at X,Y in a rendering buffer

[Ken R. <res...@sp...>]

I am basing my code on the images1 example and I have changed
the image 'partner' shape from an ellipse to a rectangle.

The partner rectangle comes out at X,Y and scales and rotates,
but the top left-hand corner of the image is always stuck at
(x,y)=3D(0,0). Only the part of the image that overlaps the=20
rectangle is visible, but that part scales and rotates properly.=20
When there is no overlap, there is no image.

I do not understand much of the the image1 example, so I am
lost as to what might be.the cause. Code is attached.

Would be most grateful for help and/or example code.

Best regards
Ken

void image ( HAGG * h , int x , int y , TCHAR * imgfilename )
   {
   if ( !loadimage ( h , imgfilename ) ) // sets image details in h
      {
      return ;
      }
   agg::rendering_buffer rbuf(h->pixels ,
                              h->frame_width ,=20
                              h->frame_height ,=20
                              -(h->frame_width * h->bytesperpixel) ) ;=20
   typedef agg::renderer_base<pixfmt>                     renderer_base;
   typedef agg::renderer_base<pixfmt_pre>                 =
renderer_base_pre;
   typedef agg::renderer_scanline_aa_solid<renderer_base> =
renderer_solid;
   pixfmt            pixf(rbuf);
   pixfmt_pre        pixf_pre(rbuf);
   renderer_base     rb(pixf);
   renderer_base_pre rb_pre(pixf_pre);
   renderer_solid    rs(rb);

   rb.clear(agg::rgba(1.0, 1.0, 1.0));

   agg::rasterizer_scanline_aa<> pf;
   agg::scanline_u8 sl;

   IMGINFO * i =3D &h->imgs [ 0 ] ;
   double imgwd =3D i->width ;       // image width
   double imght =3D i->height  ;     // image height

   agg::trans_affine src_mtx;
   src_mtx *=3D agg::trans_affine_translation(-x,-y);
   src_mtx *=3D agg::trans_affine_rotation(-h->t.angle);  // in radians
   src_mtx *=3D agg::trans_affine_scaling(h->t.scalex , h->t.scaley);
   src_mtx *=3D agg::trans_affine_translation(x,y);

   agg::trans_affine img_mtx;
   img_mtx *=3D agg::trans_affine_translation(-x,-y);
   img_mtx *=3D agg::trans_affine_rotation(-h->t.angle);
   img_mtx *=3D agg::trans_affine_scaling(h->t.scalex , h->t.scaley);
   img_mtx *=3D agg::trans_affine_translation(x,y);
   img_mtx.invert();

   typedef agg::span_allocator<color_type> span_alloc_type;
   span_alloc_type sa;
   typedef agg::span_interpolator_linear<> interpolator_type;
   interpolator_type interpolator(img_mtx);

   // "hardcoded" bilinear filter

   typedef agg::span_image_filter_rgb_bilinear<color_type, =
component_order,=20
                                               interpolator_type> =
span_gen_type;
   typedef agg::renderer_scanline_aa<renderer_base_pre, span_gen_type> =
renderer_type;

   agg::rendering_buffer rbuf_img(i->pixels ,
                                  (int)imgwd ,=20
                                  (int)imght ,=20
                                  -i->stride ) ;=20
   span_gen_type sg(sa,=20
                    rbuf_img,  // rendering buf with image pixels
                    agg::rgba_pre(0, 0.4, 0, 0.5),
                    interpolator);
   renderer_type ri(rb_pre, sg);

   agg::path_storage path; // partner rectangle
   path.move_to( x,y);
   path.line_to( x+imgwd, y );
   path.line_to( x+imgwd, y+imght);
   path.line_to( x, y+imght);
   path.close_polygon();
   agg::conv_transform<agg::path_storage> tr(path, src_mtx);
         =20
   pf.add_path(tr);
   agg::render_scanlines(pf, sl, ri);
   }
static void drawimage ( )
   {
   RECT rt ;
   GetClientRect(hwndmain, &rt);
   int width =3D rt.right - rt.left;
   int height =3D rt.bottom - rt.top;

   HAGG * h =3D gethandle ( mybuf , width , height , 4 ) ;

   settrans_scale ( h , scale ) ;
   settrans_rotate ( h , degrees ) ;
//   image ( h , 20,50 , "bmpeivor.bmp"  ) ; // does not work
   image ( h , 0,0 , "bmpeivor.bmp"  ) ;  // works

   display ( h , hwndmain ) ;  // on screen
   }