|Description||The portable pixmap format (PPM) is an image format designed to be easily exchanged between platforms which is used by Netpbm - an open-source package of graphics programs and a programming library, used mainly in the Unix world. The format is a lowest common denominator color image file format and is highly inefficient, containing a lot of information the human eye can’t even discern. The precursor to the PPM format was the PBM format which was invented by Jef Poskanzer in the 1980s as a format that allowed monochrome bitmaps to be transmitted within an email message as plain ASCII text, allowing it to survive any changes in text formatting. By the end of 1988, Poskanzer had developed the PGM and PPM formats along with their associated tools and added them to Pbmplus. The final release of Pbmplus was December 10, 1991.|
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|Technical Details||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: |
There is actually another version of the PPM format that is fairly rare: plain PPM format.
- A magic number for identifying the file type. A ppm image's magic number is the two characters P6.
- Whitespace (blanks, TABs, CRs, LFs).
- A width, formatted as ASCII characters in decimal.
- A height, again in ASCII decimal
- 6. Whitespace.
- The maximum color value (Maxval), again in ASCII decimal. Must be less than 65536 and more than zero.
- A single whitespace character (usually a newline).
- A raster of Height rows, in order from top to bottom. Each row consists of Width pixels, in order from left to right. 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 significant byte is first.
What is the NetPBM format ?
Convert PPM file