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

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

Maxim, many thanks,

I have replaced

   agg::path_storage path; // partner rectangle
    path.move_to( x,y);
    path.line_to( x+imgwd, y );
    pathmline_to( x+imgwd, y+imght);
    path.line_to( x, y+imght);
    path.close_polygon();
    agg::conv_transform<agg::path_storage> tr(path, src_mtx);
    pf.add_path(tr);
    agg::render_scanlines(pf, sl, ri);

at the and of my image proc (code of the whole proc is at
the end of my original post (and at the end of this email))

by

   double para [ 6 ]
    = { 0,100 ,  0,0 , 100.0 } ; // 3 points (0,100) (0,0) and (100,0)
   agg::trans_affine tr(para, 0, 0, imgwd, imght);
   pf.add_path(tr);
   agg::render_scanlines(pf, sl, ri);

Q1.   is this the right way?

Q2.  what should the para points be expressed as functions of
        image top-left hand corner, image width and image height, i.e.
        x,y, imgwd, imght?

My test cases includes image (x,y)=(0,0), so I defined para points
(0,100), (0,0) and (100,0) just to see what would happen.

but got compilation errors:

..\agg23\include\agg_rasterizer_scanline_aa.h(465) : error C2039: 'rewind' :
is not a member of 'trans_affine'
  ..\agg23\include\agg_trans_affine.h(88) : see declaration of
'trans_affine'

and one more very similar:  'vertex' : is not a member of 'trans_affine'

What might be the problem?

Best regards
Ken


----- Original Message -----
From: "Maxim Shemanarev" <mc...@an...>
To: <vec...@li...>
Sent: Thursday, November 17, 2005 10:31 PM
Subject: [AGG] Re: Beginner - how to put an image at X,Y in a rendering
buffer


> Transforming images is tricky, especially proper calculation of the affine
> matrix.
> But first, if you don't need to transform it you can directly copy or
blend
> the image, it will work much faster. See renderer_base<>::copy_from(),
> blend_from().
>
> For the transformer there's a simple way of calculating the matrix as a
> parallelogram, see image_perspective.cpp
>
> // Note that we consruct an affine matrix that transforms
> // a parallelogram to a rectangle, i.e., it's inverted.
> // It's actually the same as:
> // tr(0, 0, img_width, img_height, para); tr.invert();
> agg::trans_affine tr(para, 0, 0, img_width, img_height);
>
> Where "para" is double[6] that defines 3 point of the parallelogram.
>
> McSeem
>
>
> "Ken Resander" <res...@sp...> wrote in message
> news:001601c5eb0e$5e02d2c0$411faccb@KENXP...
> 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)=(0,0). Only the part of the image that overlaps the
> rectangle is visible, but that part scales and rotates properly.
> 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 ,
>                               h->frame_height ,
>                               -(h->frame_width * h->bytesperpixel) ) ;
>    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 = &h->imgs [ 0 ] ;
>    double imgwd = i->width ;       // image width
>    double imght = i->height  ;     // image height
>
>    agg::trans_affine src_mtx;
>    src_mtx *= agg::trans_affine_translation(-x,-y);
>    src_mtx *= agg::trans_affine_rotation(-h->t.angle);  // in radians
>    src_mtx *= agg::trans_affine_scaling(h->t.scalex , h->t.scaley);
>    src_mtx *= agg::trans_affine_translation(x,y);
>
>    agg::trans_affine img_mtx;
>    img_mtx *= agg::trans_affine_translation(-x,-y);
>    img_mtx *= agg::trans_affine_rotation(-h->t.angle);
>    img_mtx *= agg::trans_affine_scaling(h->t.scalex , h->t.scaley);
>    img_mtx *= 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,
>                                                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 ,
>                                   (int)imght ,
>                                   -i->stride ) ;
>    span_gen_type sg(sa,
>                     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);
>
>    pf.add_path(tr);
>    agg::render_scanlines(pf, sl, ri);
>    }
> static void drawimage ( )
>    {
>    RECT rt ;
>    GetClientRect(hwndmain, &rt);
>    int width = rt.right - rt.left;
>    int height = rt.bottom - rt.top;
>
>    HAGG * h = 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
>    }
>
>
>
>
>
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