[dev-context] regression testing: page image differences

[Sanjoy Mahajan]

>> menas that p.1 was different in the two runs, but only slightly (about
>> 0.2 dB).  Here another example with a slightly larger dB difference:

> Could it be because of the differences between lm-math and cm-math
> fonts?

Good thought.  I'm pretty sure you're right.  Here's one of the 5dB
differences.  Each pdf file uses five fonts, and the two fonts that
vary between the files are the math ones:

$ pdffonts tex/context/base/core-mat.tex/test-001-20070112.pdf > 1
$ pdffonts tex/context/base/core-mat.tex/test-001-20070123.pdf > 2
$ diff -U0 1 2

--- 1	 2007-02-05 21:29:55.000000000 -0500
+++ 2	 2007-02-05 21:29:55.000000000 -0500
@@ -4 +4 @@
-XXFRMY+CMMI12                        Type 1       yes yes yes      5  0
+URGTRZ+LMMathItalic12-Italic         Type 1       yes yes yes      5  0
@@ -7 +7 @@
-FXXUVH+CMSY10                        Type 1       yes yes yes      8  0
+DOUOBX+LMMathSymbols10-Italic        Type 1       yes yes yes      8  0

-Sanjoy

`Not all those who wander are lost.' (J.R.R. Tolkien)