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List of file formats: Difference between revisions
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These files are texture files in [http://en.wikipedia.org/wiki/Silicon_Graphics SGI] Image Format. This format supports multiple layers, transparency, compression, indexed colors, 8 bits and 16 bits per plane. Files of this format use different extensions, often to indicate the image properties, but in fact it's always the same format. The "official" extensions is <tt>*.sgi</tt>. Images with one layer are usually black/white (<tt>*.bw</tt>) or a mere alpha layer (<tt>*.a</tt>), with two layers black/white with alpha, with three layers red/green/blue (<tt>*.rgb</tt>), and with four layers red/green/blue/alpha (<tt>*.rgba</tt>). This, however, is a convention and not mandated by the image specification. SGI images can be uncompressed or [http://en.wikipedia.org/wiki/Run-length_encoding RLE-compressed], which is a lossless compression method. | These files are texture files in [http://en.wikipedia.org/wiki/Silicon_Graphics SGI] Image Format. This format supports multiple layers, transparency, compression, indexed colors, 8 bits and 16 bits per plane. Files of this format use different extensions, often to indicate the image properties, but in fact it's always the same format. The "official" extensions is <tt>*.sgi</tt>. Images with one layer are usually black/white (<tt>*.bw</tt>) or a mere alpha layer (<tt>*.a</tt>), with two layers black/white with alpha, with three layers red/green/blue (<tt>*.rgb</tt>), and with four layers red/green/blue/alpha (<tt>*.rgba</tt>). This, however, is only a convention and not mandated by the SGI image specification. SGI images can be uncompressed or [http://en.wikipedia.org/wiki/Run-length_encoding RLE-compressed], which is a lossless compression method. | ||
FlightGear uses [http://plib.sourceforge.net/ plib] to read SGI images. They must not use 16 bits per plane and | FlightGear uses [http://plib.sourceforge.net/ plib] to read SGI images. They must not use 16 bits per plane and must have side lengths of 2<sup>n</sup>x2<sup>m</sup> (powers of 2). For example: 64x64, 256x256 or 128x2048. Note that other sizes will '''not''' work, and FlightGear will use a red/white chequered texture instead! FlightGear textures ''shall'' be RLE-compressed, and as 'aggressively' as possible. | ||
All better graphics applications should be able to read and write the format, but often they load SGI images without problems, but only write them properly when the <tt>*.sgi</tt> extension is used. Here are some free applications that create SGI images, along with some usage notes: | All better graphics applications should be able to read and write the format, but often they load SGI images without problems, but only write them properly when the <tt>*.sgi</tt> extension is used. Here are some free applications that create SGI images, along with some usage notes: | ||
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This creates SGI images with RLE compression by default. | This creates SGI images with RLE compression by default. | ||
= *.stg = | = *.stg = | ||