Here's a quick fix for the writing of the file, as well...
Before making the fix below, go to line 721 and change the '1' to a '2' !
721: ifd[RESOLUTION_UNIT] = 1
becomes
721: ifd[RESOLUTION_UNIT] = 2
Then make the changes listed below. This is consistent with those changes.
This is a quick and dirty fix that I have not tested extensively, but it
quickly allows me to read and write TIFF images with both the PIL and
Photoshop, and each can see the DPI as set by the other. It fixes the problem
I've had with PIL reading/writing TIFFs. Thanks, Florian!
Regards,
Gary Bloom
Sales Engineer
Sefas Innovation
www.sefas.com
============
[Image-SIG] BUG: PIL DPI trouble - fix for TIFF files (PIL 1.1.6)
Florian Höch lists+Image_SIG at hoech.org
Fri Oct 5 00:05:16 CEST 2007
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PIL only adds a dpi entry in the info dictionary if no resolution unit
is specified in the TIFF file. This seems to be because of a
misinterpretation of resolution unit values: they have a different
meaning than in a JPEG file. JPEG: 0 = None; 1 = inches; 2 = cm. TIFF: 1
= None; 2 = inches; 3 = cm (see
http://www.awaresystems.be/imaging/tiff/tifftags/resolutionunit.html and
http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html)
Here's a quick fix:
Open TiffImagePlugin.py and go to line 577. Change the code:
xres = getscalar(X_RESOLUTION, (1, 1))
yres = getscalar(Y_RESOLUTION, (1, 1))
if xres and yres:
xres = xres[0] / (xres[1] or 1)
yres = yres[0] / (yres[1] or 1)
resunit = getscalar(RESOLUTION_UNIT, 1)
if resunit == 2: # Inches
self.info["dpi"] = xres, yres
elif resunit == 3: # Centimeters
self.info["dpi"] = xres * 2.54, yres * 2.54
else: # No absolute unit of measurement.
self.info["resolution"] = xres, yres
Regards,
Florian Hoech
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