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