How to stop GhostScript replacing Times-Roman with NimbusRomNo9L-Regu (on Windows)
I am using Ghostscript v9.07 on Windows 7 (x64) to convert PostScript files into PDFs. Inside the PostScript files, the fonts Times-Roman and Times-Bold are used - this can be seen in the PostScript plain-text:
/Times-Roman findfont 24.00 scalefont setfont
.
.
.
/Times-Bold findfont 24.00 scalefont setfont
.
.
.
(This is extremely common in PostScript output from TeX.)
When I convert the PostScript to PDF using Ghostscript, Ghostscript uses the Nimbus-Roman font-family.
GPL Ghostscript 9.07 (2013-02-14)
Copyright (C) 2012 Artifex Software, Inc. All rights reserved.
This software comes with NO WARRANTY: see the file PUBLIC for details.
Loading NimbusRomNo9L-Regu font from %rom%Resource/Font/NimbusRomNo9L-Regu... 39
38016 2393624 2695216 1387174 4 done.
Loading NimbusRomNo9L-Medi font from %rom%Resource/Font/NimbusRomNo9L-Medi... 39
38016 2453738 2695216 1390537 4 done.
This output suggests that it is loading the font-family from resources embedded in the executable. In any case, it isn't loading it from the PostScript file so it is either from the application's distribution or the operating system.
The result looks abysmal in every PDF viewer I have tried, regardless of font-smoothing settings.
I cannot understand it. The resulting PDF's text is not rasterised - you can select it and cut and paste it and the file-size alone shows that it is still real text - so I can only conclude that this is a quirk of the Nimbus-Roman typeface.
There is absolutely no reason to use that typeface but, no matter what I do, I cannot seem to get Ghostscript to use a Times-Roman (or equivalent) typeface from the Windows font set.
I tried the -sFONTPATH switch (alternatively called sFONTDIR on some sites - I tried both) to no avail and I went looking for the fontmap file to try hacking that but didn't find one for Windows - only fontmaps for other operating systems in the install directory.
How can I change this behaviour and stop Ghostscript from using the awful font?
The way to have Ghostscript use a specific font, rather than a substitute, is to embed the font in the input.
This:
/Times-Roman findfont 24.00 scalefont setfont
merely requests a font (and size), it does not include the font data. In the absence of the font, Ghostscript is forced to use a substitute font.
On Windows, Ghostscript uses the ROM file system, and does not ship with the support files. If you want to use those you can pull them from Git, and then use the -I switch. That will allow you to alter cidfmap which controls the CIDFonts known to Ghostscript, and fontmap.GS which controls the regular fonts known.
However, I don't see the result you do with the apparently bitmapped font. Perhaps you should try a newer version of Ghostscript. Or post an original PostScript program and converted PDF file so it would be possible to examine them.
[edit starts here]
OK so basically there's some problems with what you've put up above. The screenshot you have there is from page 1, but the 'font substitution', ie the loading of NimbusRoman-Regular and NimbusRoman-Bold (on current versions of Ghostscript) take place on page 5. Clearly the 'substitution' on page 5 can't affect what's on page 1. You would have seen that if you hadn't set -dBATCH, moral; when debugging a problem, keep the command line simple.
The actual 'problem' is that the PostScript program uses a type 3 bitmap font for all the text, the font being defined in the body of the program.
In short, the text is a crappy bitmap font because that's the way the PostScript has been created, it contains a crappy bitmap font and insists on using it (FWIW it appears to have been rendered at 300 dpi).
In fact the only text in the document which is scalable is the very text which uses Times-Roman (not a substitution, it uses the font from the interpreter instead of the bitmap font).
This is the text for the figure at the top of the page; 'point', 'p', 'X', 'line', 'Y', 'u', 'W'. This has been included as an EPS (originally called ray_space.eps) into the document, which is why it uses real scalable fonts. If you zoom in on the top of page 5 you will see that the scalable fonts continue to look smooth (the body of the figure) while the bitmapped font (the figure title for example) look bitmapped.
There's nothing you can do about that, essentially, other than recreate the PostScript from the original DVI document. This is not a bug (or at least, not a Ghostscript bug).
[and another edit...]
I'm afraid its not really simple.
There are 26 fonts named /Fa to /Fx, I am unsure why this is the case, since each font is capable of containing 255 glyphs yet most do not (at the same time, they don't just contain two glyphs either). There seems no good reason for the fonts being encoded as they are.
The program uses each font as it requires it, switching fonts when it needs different glyphs. Eg:
1 0 bop
392 319 a Fx (An)21 b(In)n(tro)r(duction)g(to)h(Pro)t(jectiv)n
(e)h(Geometry)670 410 y(\(for)f(computer)f(vision\))
815
561 y Fw(Stan)c(Birc)o(h\014eld)74 754 y Fv(1)67 b(In)n(tro)r(duction)
74 856 y Fu(W)l(e)
The 'Fx' and 'Fw' calls load the font dictionary which is then used by the following code. Frankly the Tex PostScript is difficult to figure out, one might almost think it was designed to be obfuscated.
Identifying which 2-byte pair beginning with 'F' require removing or replacing, and which do not (eg ASCII encoded image data) would be tricky. In addition the glyphs are rendered flipped in the y axis (to match the transformation matrix in use) so you would have to adjust the FontMatrix similarly for a substitute font.
If the fonts in these TeX font dictionaries always contained the same glyphs, it would be possible to define a set of substitute fonts (/Fa to /Fx) which could be used instead. These would need to be loaded into the TeXDict dictionary to replace the ones defined in the header of the progtam of course.
I'm not saying its impossible, but it would be a good amount of research effort to figure out what would be possible, and then a good amount of coding to implement it.