Re: Transparent background with PNG
- To: mathgroup at smc.vnet.net
- Subject: [mg96920] Re: Transparent background with PNG
- From: Stonewall Ballard <stoneyb at gmail.com>
- Date: Fri, 27 Feb 2009 06:13:24 -0500 (EST)
- References: <gnm1o0$hgg$1@smc.vnet.net>
On Feb 20, 5:47 am, replicator... at gmail.com wrote:
> Hi,
>
> how can I save an image to PNG format (eg. a simple plot), with the
> (white) background being transparent? I understand that PNG export
> supports alpha channel, but have no clue how to instruct Mathematica
> to exploit it.
This seems to be excessively obscure, but I got a png with a
transparent background this way (in V7):
plotImage = Plot[x^2, {x, 0, 2}]
bkgImage =
Image[ConstantArray[{0., 0., 0., 0.},
Reverse[ImageDimensions[plotImage]]], ColorSpace -> "RGB"]
compImage = ImageCompose[bkgImage, plotImage]
Export["~/Desktop/compImage.png", compImage]
It seems that composing the graphic against a transparent image gives
it an alpha channel.