[Scilab-users] {EXT} Fwd: plotting dots vs xfarc

[P M]

Hi,

I think I'll modify the pixels in the image....like: img(x,y) = 255;

If necessary I will also change some neighboured pixels to enlarge the
"dot"-size.

I do not need them blue...this was just to demonstrate that

      plot(x,y,'o')  ( = white)

and

     xfarc(x_arc,y_arc, w_arc,h_arc,0,360*64)   (= blue)

do not always plot at the same location....even all coordinates are just
simple integers.

So far I could see, this does not change, even if one changes the
pixel_drawing_mode attribute.

Thanks for your ideas,
Philipp

Am Do., 1. Okt. 2020 um 10:25 Uhr schrieb Antoine Monmayrant <
antoine.monmayrant at laas.fr>:

>
> On 01/10/2020 09:05, Dang Ngoc Chan, Christophe wrote:
> > Hello,
> >
> >> De la part de P M
> >> Envoyé : mercredi 30 septembre 2020 16:50
> >>
> >> exact dot-coordinates, drawn as filled circles.
> >> All pixel coordinates of such an area would have to have exactly one
> single pixel value.
> >> The resulting graphic right now is stored via:      xs2bmp.
> >> [...]
> >> - It seems that the resulting pixels of the dot in the final image are
> not equally colored.
> > I suspect the following thing: pixels are squares, not dots.
> >
> > So it may be that xs2bmp somehow inter-/extrapolate the colours.
> > You then have a "leak" between the coloured pixel and its neighbours.
> >
> > You may try to draw squares of the exact size of the final pixel (e.g.
> 1/320 width and 1/200 height of the graphical window for a 320 × 200 raster
> picture).
> >
> > You may also try some functions from the image processing toolboxes.
> Well, another approach would be to:
> - use Matplot to display your image as a matrix, let's say [0:255] range.
> - modify the data in the matrix to be displayed where you went to get
> your "dot": like your change your data to 256
> - use a colormap that is grayscale from [0:255] and has a fancy color
> for 256 (blue?).
>
> If you do this, you should get a perfect co-registration of your image
> and your "overlayed" markers.
> Of course, your markers will not be circular dots, just a single pixel
> with what I described above, but you can also generate your own shapes
> (bigger squares, crosses, ~circles), provided that you use an odd number
> of pixels.
>
> Hope it helps,
>
> Antoine
>
> >
> > Hope this helps
> >
> > Regards
> >
> > --
> > Christophe Dang Ngoc Chan
> > cdang at wanadoo.fr
> >
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