Export[..., ImageResolution, ... ImageSize]

[Scot Martin]

Anyone have insight on this problem with image resolution in version 7?

SetDirectory@NotebookDirectory[];

plot = Plot[x, {x, 0, 10}];

Export["plot.gif",plot,ImageSize->5*72,ImageResolution->300]

The export command seems to ignore ImageResolution.

Here is what used to work in V5.2 of Mathematica:

Export["plot.gif",plot,ImageResolution->300]

This "plot.gif" in V7 now has the problem that all of the ticks and so forth
have become very small, i.e., they were not scaled properly. Apparently,
Mathematica combined ImageSize and ImageResolution by scaling the image to
(300/72)*5*72, without proportionate magnification of the ticks. [This was
not a problem in earlier versions of Mathematica, e.g., V5.2.]

Here is a messy workaround:

Export["plot.gif", Magnify[Show[FullGraphics@plot, Options[plot,
AspectRatio]], 300/72],ImageResolution -> 300]

My question for the group: Am I missing a simple solution to this problem
instead of the messy work around?

Thanks for any help and insight!

[Scot Martin]

[Alexey]

Hello,

The solution for your problem is (code for Mathematica 7.0.1):

$HistoryLength = 0;

plot = Plot[x, {x, 0, 10}]

g = Rasterize[plot, ImageResolution -> 300]
dims = g[[1, 1]] // Dimensions
ggg = Graphics[g[[1]], ImageSize -> dims[[{2, 1}]]];
Export["C:/plot.gif", Image[ggg]]

This problem has already been discussed in this newsgroup. In short,
the explanation is as follows:

1) Graphics has default width 360 pixels and in this way the quality
will be only 360 pixels width even if Raster[] inside Graphics[]
contains much more points. And resizing does not help. This also
directly affects Export[]... :( But Image[] always has true dimensions
and preserves quality. I discussed it in details here:

http://groups.google.ru/group/comp.soft-sys.math.mathematica/msg/16eea8a5d0da24b4
http://tinyurl.com/njmpro

2) I have not found a perfect way how to change *default* width of
Graphics[] (without using ImageSize). I discussed it here:

http://tinyurl.com/l288ne

3) There are some undocumented functions for working with raster
graphics that may help. See here:

http://groups.google.ru/group/comp.soft-sys.math.mathematica/msg/d67bc8ab0d2ebd43
http://groups.google.ru/group/comp.soft-sys.math.mathematica/browse_frm/thread/df0892da9341f569/c4cfa6889eb38531%3Fq%3D%23c4cfa6889eb38531&ei=U0xoS-XWCqekQ5GklYsI&sa=t&ct=res&cd=4&source=groups&usg=AFQjCNGb4qaPzq783mSkG6a2HaRlrgp7Xg

4) I have created a function Raster2Image that converts
Graphics[Raster[]] to Image with preserving quality
(as opposed to Image[Graphics]):

Raster2Image = Image[Part[#, Sequence @@ Position[#, _Raster]
[[1]], 1], ColorSpace -> "RGB"] &;

I also created function fix4Graphics that fixes loosing quality with
Export[]:

fix4Graphics = Append[#, ImageSize -> Reverse[Take[Dimensions
[Part[#, Sequence @@ Position[#, _Raster][[1]], 1]], 2]]] &;