Hello,
While experimenting with code to create image from data, I encountered
an issue with the regexp in `image-type-header-regexps' used to
auto-detect PBM image type from the first bytes of image data. That is:
"\\`P[1-6]\\(?:\
\\(?:\\(?:#[^\r\n]*[\r\n]\\)*[[:space:]]\\)+\
\\(?:\\(?:#[^\r\n]*[\r\n]\\)*[0-9]\\)+\
\\)\\{2\\}"
Here is a simple recipe to illustrate the issue:
In *scratch* buffer eval:
-------------------------
;; Get content of a pbm file.
(setq test-data
(with-current-buffer
(find-file-noselect "[YourEmacsPath]/etc/images/splash.pbm")
(prog1 (buffer-substring-no-properties (point-min) (point-max))
(kill-buffer (current-buffer)))))
;; Check string data fail for pbm image-type!
(image-type-from-data test-data)
nil
;; With a temp buffer current, the same test works!
(with-temp-buffer
(image-type-from-data test-data))
pbm
-------------------------
After further digging, I found that the problem might be due to the use
of the [:space:] character class whose meaning, according to the manual,
depends on the syntax of whitespace characters setup in current buffer.
So, using discrete values in place of syntax class seems to solve the
issue:
(setcar (nth 1 image-type-header-regexps)
"\\`P[1-6]\\(?:\
\\(?:\\(?:#[^\r\n]*[\r\n]\\)*[ \t\r\n]\\)+\
\\(?:\\(?:#[^\r\n]*[\r\n]\\)*[0-9]\\)+\
\\)\\{2\\}")
(image-type-from-data test-data)
pbm
I attached a patch proposal.
Hope it will help.
Regards