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

SourceForge Headquarters 1320 Columbia Street Suite 310 San Diego, CA 92101 +1 (858) 422-6466

Hi Ken,

Sorry for the delay, I was kinda busy last time. and besides, I'm suffering 
from constant problems with the Internet (Verizon in NYC sucks, I'm 
switching to cable).

Well, I understand everyone is busy, but could someone else answer the 
questions too?

First, you need to understand that a path is the primary thing in AGG. 
Without path you can't draw anything. So that, to rotate an image you need 
to create a respective path as if you wanted to fill this area with a solid 
color. And then, you just substitute an image renderer for your solid fill. 
Obviously, to transform the whole image you need to create a parallelogram 
path (a rectangle in particular). You can do that calculating the points 
manually:
ras.move_to_d(x1, y1);
ras.line_to_d(x2, y2);
. . .
You you can use transformations.
Next, trans_affine doesn't have any "VertexSource" interface, it can't 
generate vertices. It can only transform them: affine.transform(&x, &y); To 
add affine transformer into your pipeline you also need conv_transform:

double para [ 6 ] = { 0,100 ,  0,0 , 100,0 } ; // 3 points (0,100) (0,0) and 
(100,0)
agg::trans_affine mtx(para, 0, 0, imgwd, imght);
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, agg::trans_affine> trans(path, mtx);

pf.add_path(trans); // Note you add "trans"

Then, if you want your image to fit exactly your parallelogram path (you 
also may want to do differently!), you need to create a copy of the matrix 
and invert it:

agg::trans_affine img_mtx(mtx);
img_mtx.invert();

Well, I realize that it all is pretty confusing. But this kind of a design 
is most flexible.

McSeem

"Ken Resander" <res...@sp...> wrote in message 
news:001201c5ebf8$efea65a0$4f1faccb@KENXP...
> 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
>>    }
>>
>>
>>
>>
>>
>> -------------------------------------------------------
>> This SF.Net email is sponsored by the JBoss Inc.  Get Certified Today
>> Register for a JBoss Training Course.  Free Certification Exam
>> for All Training Attendees Through End of 2005. For more info visit:
>> http://ads.osdn.com/?ad_id=7628&alloc_id=16845&op=click
>> _______________________________________________
>> Vector-agg-general mailing list
>> Vec...@li...
>> https://lists.sourceforge.net/lists/listinfo/vector-agg-general
>>
>
>
>
> -------------------------------------------------------
> This SF.Net email is sponsored by the JBoss Inc.  Get Certified Today
> Register for a JBoss Training Course.  Free Certification Exam
> for All Training Attendees Through End of 2005. For more info visit:
> http://ads.osdn.com/?ad_id=7628&alloc_id=16845&op=click 