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Re: Re: overimpose graphics on an imported image


Alessandro,

A bit more straightforward is the following:

img = Import["http://sipi.usc.edu/database/misc/5.1.12.tiff";];

{nx, ny} =  ImageDimensions[img];

Show[{Rasterize[img], Graphics@{Red, Opacity[0.5], Disk[{nx/3, 2 ny/3},
35]}}]

Using the Rasterize command the image is converted to Graphics  first.
(Thank to Mariusz Jankowski)

regards, Maarten




-----Original Message-----
From: alexxx.magni at gmail.com [mailto:alexxx.magni at gmail.com]
Sent: Tuesday, 05 January, 2010 07:50
To: mathgroup at smc.vnet.net
Subject: [mg106267] [mg106232] Re: overimpose graphics on an imported image

thank you for your help!
It works, although it needs this further refinement:

ImageCompose[i1, {Graphics[{Red,
    Rectangle[{xmin, ny - ymin}, {xmax, ny - ymax}]},
   PlotRange -> {{0, nx}, {0, ny}}], 0.5}]

if I want to be consistent with coordinates given in other Mathematica
functions
(e.g. ImageTake[i1, {ymin, ymax}, {xmin, xmax}] which I use on the
same image...)

I just would like the coordinates were less confusing in M !

alessandro



On 2 Gen, 11:04, Patrick Scheibe <psche... at trm.uni-leipzig.de> wrote:
> Hi,
>
> tell Mathematica about your plotting-range:
>
> img = Import["http://sipi.usc.edu/database/misc/5.1.12.tiff";];
> {nx, ny} = ImageDimensions[img];
> ImageCompose[img, {Graphics[{Red, Rectangle[{0, 0}, {nx/2, ny/2}]},
>    PlotRange -> {{0, nx}, {0, ny}}], 0.5}]
>
> Cheers
> Patrick
>
> On Fri, 2010-01-01 at 05:37 -0500, alexxx.ma... at gmail.com wrote:
> > hi people,
> > I wonder if it is just me being dumb, but I'm unable to perform what
I
> > thought was a very simple operation:
>
> > having imported an image of (Lx,Ly) pixels, draw above it an empty
> > rectangle at coordinates (x0,y0) (x1,y1) (say, lower left and upper
> > right corners).
>
> > Say for example that I want to overimpose on image i1 a rectangle
> > covering a 10% portion, if I use this:
>
> > ImageCompose[i1, Graphics[Rectangle[{0, 0}, {0.1*Lx, 0.1*Ly}]]]
>
> > I have (apart from a filled rectangle instead of empty, but I can
deal
> > with it later)
> > a huge rectangle covering all of it!
> > How these coordinates interact?
>
> > Thanks for any help...
>
> > Alessandro Magni




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