Ghostscript -- convert PS to PNG, rotate, and scale - png

Question

I have an application that creates very nice data plots rendered in PostScript with letter size and landscape mode. An example of the input file is at http://febo.com/uploads/blip.ps. [ Note: this image renders properly in a viewer, but the PNG conversion comes out with the image sideways. ] I need to convert these PostScript files into PNG images that are scaled down and rotated 90 degrees for web presentation.
I want to do this with ghostscript and no other external tool, because the conversion program will be used on both Windows and Linux systems and gs seems to be a common denominator. (I'm creating a perl script with a "PS2png" function that will call gs, but I don't think that's relevant to the question.)
I've searched the web and spent a couple of days trying to modify examples I've found, but nothing I have tried does the combination of (a) rotate, (b) resize, (c) maintain the aspect ratio and (d) avoid clipping.
I did find an example that injects a "scale" command into the postscript stream, and that seems to work well to scale the image to the desired size while maintaining the aspect ratio. But I can't find a way to rotate the resized image so that the, e.g., 601 x 792 point (2504 x 3300 pixel) postscript input becomes an 800 x 608 pixel png output.
I'm looking for the ghostscript/postscript fu that I can pass to the gs command line to accomplish this.
I've tried gs command lines with various combinations of -dFIXEDMEDIA, -dFitPage, -dAutoRotatePages=/None, or /All, -c "<> setpagedevice", changing -dDISPLAYWIDTHPOINTS and -dDISPLAYHEIGHTPOINTS, -g[width]x[height], -dUseCropBox with rotated coordinates, and other things I've forgotten. None of those worked, though it wouldn't surprise me if there's a magic combination of some of them that will. I just haven't been able to find it.
Here is the core code that produces the scaled but not rotated output:
## "$molps" is the input ps file read to a variable
## insert the PS "scale" command
$molps = $sf . " " . $sf . " scale\n" . $molps;
$gsopt1 = " -r300 -dGraphicsAlphaBits=4 -dTextAlphaBits=4";
$gsopt1 = $gsopt1 . " -dDEVICEWIDTHPOINTS=$device_width_points";
$gsopt1 = $gsopt1 . " -dDEVICEHEIGHTPOINTS=$device_height_points";
$gsopt1 = $gsopt1 . " -sOutputFile=" . $outfile;
$gscmd = "gs -q -sDEVICE=pnggray -dNOPAUSE -dBATCH " . $gsopt1 . " - ";
system("echo \"$molps\" \| $gscmd");
$device_width_points and $device_height_points are calculated by taking the original image size and applying the scaling factor $sf.
I'll be grateful to anyone who can show me the way to accomplish this. Thanks!

Answer 1

Better Answer:
You almost had it with your initial research. Just set orientation in the gs call:
... | gs ... -dAutoRotatePages=/None -c '<</Orientation 3>> setpagedevice' ...
cf. discussion of setpagedevice in the Red Book, and ghostscript docs (just before section 6.2)
Original Answer:
As well as "scale", you need "rotate" and "translate", not necessarily in that order.
Presumably these are single-page PostScript files?
If you know the bounding box of the Postscript, and the dimensions of the png, it is not too arduous to calculate the necessary transformation. It'll be about one line of code. You just need to ensure you inject it in the correct place.
Chapter 6 of the Blue Book has lots of details
A ubc.ca paper provides some illustrated examples (skip to page 4)
Simple PostScript file to play around with. You'll just need the three translate,scale,rotate commands in some order. The rest is for demonstrating what's going on.
%!
% function to define a 400x400 box outline, origin at 0,0 (bottom left)
/box { 0 0 moveto 0 400 lineto 400 400 lineto 400 0 lineto closepath } def
box clip % pretend the box is our bounding box
clippath stroke % draw initial black bounding box
(Helvetica) findfont 50 scalefont setfont % setup a font
% draw box, and show some text # 100,100
box stroke
100 100 moveto (original) show
% try out some transforms
1 0 0 setrgbcolor % red
.5 .5 scale
box stroke
100 100 moveto (+scaled) show
0 1 0 setrgbcolor % green
300 100 translate
box stroke
100 100 moveto (+translated) show
0 0 1 setrgbcolor % blue
45 rotate
box stroke
100 100 moveto (+rotated) show
showpage
It may be possible to insert the calculated transformation into the gs commandline like this:
... | gs ... -c '1 2 scale 3 4 translate 5 6 rotate' -# ...

Answer 2

Thanks to JHNC, I think I have it licked now, and for the benefit of posterity, here's what worked. (Please upvote JHNC, not this answer.)
## code to determine original size, scaling factor, rotation goes above
my $device_width_points;
my $device_height_points;
my $orientation;
if ($rotation) {
$orientation = 3;
$device_width_points = $ytotal_png_pt;
$device_height_points = $xtotal_png_pt;
} else {
$orientation = 0;
$device_width_points = $xtotal_png_pt;
$device_height_points = $ytotal_png_pt;
}
my $orientation_string =
" -dAutoRotatePages=/None -c '<</Orientation " .
$orientation . ">> setpagedevice'";
## $ps = .ps file read into variable
## insert the PS "scale" command
$ps = $sf . " " . $sf . " scale\n" . $ps;
$gsopt1 = " -r300 -dGraphicsAlphaBits=4 -dTextAlphaBits=4";
$gsopt1 = $gsopt1 . " -dDEVICEWIDTHPOINTS=$device_width_points";
$gsopt1 = $gsopt1 . " -dDEVICEHEIGHTPOINTS=$device_height_points";
$gsopt1 = $gsopt1 . " -sOutputFile=" . $outfile;
$gsopt1 = $gsopt1 . $orientation_string;
$gscmd = "gs -q -sDEVICE=pnggray -dNOPAUSE -dBATCH " . $gsopt1 . " - ";
system("echo \"$ps\" \| $gscmd");
One of the problems I had was that some options apparently don't play well together -- for example, I tried using the -g option to set the output size in pixels, but in that case the rotation didn't work. Using the DEVICE...POINTS commands instead did work.