Re: Precise bitmaps
- To: mathgroup at smc.vnet.net
- Subject: [mg96729] Re: Precise bitmaps
- From: David Bailey <dave at removedbailey.co.uk>
- Date: Mon, 23 Feb 2009 05:01:16 -0500 (EST)
- References: <gnq6ni$83g$1@smc.vnet.net>
Diamond, Mark wrote:
> A question was asked back in 2005 about precise bitmaps. I have a similar
> question with regard to Mathematica version 7.
>
> Looking at the new image-manipulation functions in V7, I expected this to be
> quick ... I'd like to be able to create a series of stimuli for use in an
> experiment. The first step in creating the stimuli is to create a 512 x 512
> greyscale image with a white background and which contains the drawn
> objects.
>
> I tried the following to create a JPEG image with dimensions 128x128 ...
>
> circ=Graphics[Circle[{0,0},62]]
> rasterCirc=Rasterize[circ,RasterSize->{128,128}]
> Export["circle.jpg",rasterCirc]
>
> but instead the image dimensions are 360 x 363 pixels. I had also hoped that
> I could obtain an antialiased arc but the only antialiasing option seems to
> be for Style, which then produces a non-Graphics object.
>
> Can anyone see a simple (i.e., not very low-level programming) solution to
> the problem within Mathematica? What have I missed conceptually that would
> explain the 360x363 pixel dimensions instead of my expected 128x128? And is
> there a way to obtain the anti-aliased circle?
>
> Cheers,
>
> Mark Diamond
>
>
>
The problem is that circ is a graphics object of much lower resolution -
you have to force it to be the size that you want to rasterize:
circ = Graphics[Circle[{0, 0}, 62], ImageSize -> {512, 512}]
rasterCirc = Rasterize[circ, RasterSize -> {512, 512}]
Export["circle.jpg", rasterCirc]
David Bailey
http://www.dbaileyconsultancy.co.uk