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Forums » Archive » ppm and pnm files 
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Joined: 2/25/2003
Posts: 334
Posted on Thursday, February 27, 2003 8:41:00 PM
у меня есть набор PPM и PNM.
Я знаю, что это графика, а точнее нужные картинки для проги.
Мне нужно эти файлы отредактировать в фотошопе, или еще где-то. Но их даже не могу посмотреть, только через соответственную джава-прогу.
Что делать? Можно ли как нибудь преобразовать в jpeg или другой формат, а потом обратно? Как?
Joined: 1/10/2003
Posts: 115
Posted on Thursday, February 27, 2003 9:07:00 PM
Google как всегда рулит.


Joined: 12/26/2001
Posts: 2250
Posted on Thursday, February 27, 2003 9:07:00 PM
Почти любой дистрибутив линукса содержит набор утилит для работы с
ppm (portable pixmap format) графикой:

ppm(5) ppm(5)

ppm - portable pixmap file format

The portable pixmap format is a lowest common denominator
color image file format.

It should be noted that this format is egregiously ineffi-
cient. It is highly redundant, while containing a lot of
information that the human eye can't even discern. Fur-
thermore, the format allows very little information about
the image besides basic color, which means you may have to
couple a file in this format with other independent infor-
mation to get any decent use out of it. However, it is
very easy to write and analyze programs to process this
format, and that is the point.

It should also be noted that files often conform to this
format in every respect except the precise semantics of
the sample values. These files are useful because of the
way PPM is used as an intermediary format. They are
informally called PPM files, but to be absolutely precise,
you should indicate the variation from true PPM. For
example, "PPM using the red, green, and blue colors that
the scanner in question uses."

The format definition is as follows.

A PPM file consists of a sequence of one or more PPM
images. There are no data, delimiters, or padding before,
after, or between images.

Each PPM image consists of the following:

- A "magic number" for identifying the file type. A pgm
file's magic number is the two characters "P6".

- Whitespace (blanks, TABs, CRs, LFs).

- A width, formatted as ASCII characters in decimal.

- Whitespace.

- A height, again in ASCII decimal.

- Whitespace.

- The maximum color value (Maxval), again in ASCII deci-
mal. Must be less than 65536.

- Newline or other single whitespace character.

- A raster of Width * Height pixels, proceeding through
the image in normal English reading order. Each pixel
is a triplet of red, green, and blue samples, in that
order. Each sample is represented in pure binary by
either 1 or 2 bytes. If the Maxval is less than 256, it
is 1 byte. Otherwise, it is 2 bytes. The most signifi-
cant byte is first.

- In the raster, the sample values are proportional to the
intensity of the CIE Rec. 709 red, green, and blue in
the pixel. A value of Maxval for all three samples rep-
resents CIE D65 white and the most intense color in the
color universe of which the image is part (the color
universe is all the colors in all images to which this
image might be compared).

- Characters from a "#" to the next end-of-line, before
the maxval line, are comments and are ignored.

Note that you can use pnmdepth to convert between a the
format with 1 byte per sample and the one with 2 bytes per
There is actually another version of the PPM format that
is fairly rare: "plain" PPM format. The format above,
which generally considered the normal one, is known as the
"raw" PPM format. See pbm(5) for some commentary on how
plain and raw formats relate to one another.

The difference in the plain format is:
Joined: 7/20/2002
Posts: 8934
Posted on Monday, March 3, 2003 4:36:00 PM
skachai progu IrfanView, ona delaet prosmotr i conversion v GIF/JPEG/whatever.
Joined: 2/25/2003
Posts: 334
Posted on Monday, March 3, 2003 5:24:00 PM
пасиба всем,
я уже качнула какую то прогу для "type convertion"
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