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diff --git a/imdi/Readme.txt b/imdi/Readme.txt new file mode 100644 index 0000000..a12d649 --- /dev/null +++ b/imdi/Readme.txt @@ -0,0 +1,114 @@ + +This is the development area for IMDI, the +Integer Multi-Dimensional Interpolation routines. + +They provide a flexible and high performance +system for applying color transforms to typical +raster pixel data. Because they provide a means of +applying arbitrary combination dependent mappings +of multi-channel pixel data, there are many other +possible uses for these sorts of routines as well, +including high quality matting/compositing. For instance, +one could create a smooth, proportional "chroma key" +type of matt for matting one RGB image onto another +by creating a 6 channel to 3 dimensional transform, +that its applied to each pair of pixels from the +source images and produces one combined output pixel. +Additional input or output alpha channels are easy +to add by simply adding more input and/or output +dimensions. The matting calculatons can be almost +arbitrarily complex, and the imdi will apply them +to the pixel data at very high speed. + +The system has two parts, one that generates taylored, +optimised source code for the transformation kernels, +and the run time code that matches a transform request +to a compiled kernel, and initialises the appropriate +run time lookup tables. + +The kernel source generator is intended to accomodate +various optimisations, such as assembly code, vector +instruction set (ie. MMX, AltiVec etc.) versions, but +at present only generates the more portable 'C' code +kernels. + +Both 8 bit per component and 16 bit per component +pixel data is handled, up to 8 input and output +dimensions (but this limit could be trivially raised). + +imdi_make.exe is the module that triggers the generation of + optimised source code as configured for the color spaces + and pixel formats selected. By default creates + a single imdi_k.c and imdi_k.h file, but if + given the -i flag, creates a separate file + for each kernel variant. + +cgen.c C code generator module. + +itest.c regresion test routine. + Normally runs speed and accuracy tests for + all configured kernel variants. + The -q flag makes it run quicker, + but makes the benchmarking inacurate, + the -s flag will cause it to stop + if any routine has unexpectedly low + accuracy. + +cctiff.c is the utility that takes an ICC device + profile link, and converts a TIFF file + from the input colorspace to the output + space. Both 8 bit and 16 bit TIFF files + are handled, as well as colorspaces up to + 8 channels in and out. + This accepts either a device link ICC profile, + or links an input and output devce ICC profile + to define the color transform. + + +greytiff.c is a utility similar to cctiff, that + is an example of how to colorimetrically + convert an RGB file into a monochrome RGB file. + + + +Misc. Notes +----------- + + ITU-T Rec. T.42 specifies the ITULAB encoding in terms of a range + and offset for each component, which are related to the minimum and + maximum values as follows: + + minimum = - (range x offset) / 2^n - 1 + maximum = minimum + range + + The Decode field default values depend on the color space. For the + ITULAB color space encoding, the default values correspond to the + base range and offset, as specified in ITU-T Rec. T.42 [T.42]. The + following table gives the base range and offset values for + BitsPerSample=8 and 12, and the corresponding default minimum and + maximum default values for the Decode field, calculated using the + equations above when PhotometricInterpetation=10. + + +-----------------------------------------------+ + | ITU-T Rec. T.42 | Decode | + +---------+-----------| base values | default values | + | BitsPer + Component +------------------+----------------------------+ + | -Sample | | Range | Offset | Min | Max | + +---------+-----------+--------+---------+--------------+-------------+ + | 8 | L* | 100 | 0 | 0 | 100 | + | +-----------+--------+---------+--------------+-------------+ + | | a* | 170 | 128 | -21760/255 | 21590/255 | + | +-----------+--------+---------+--------------+-------------+ + | | b* | 200 | 96 | -19200/255 | 31800/255 | + +---------+-----------+--------+---------+--------------+-------------+ + | 12 | L* | 100 | 0 | 0 | 100 | + | +-----------+--------+---------+--------------+-------------+ + | | a* | 170 | 2048 | -348160/4095 | 347990/4095 | + | +-----------+--------+---------+--------------+-------------+ + | | b* | 200 | 1536 | -307200/4095 | 511800/4095 | + +---------+-----------+--------+---------+--------------+-------------+ + + For example, when PhotometricInterpretation=10 and BitsPerSample=8, + the default value for Decode is (0, 100, -21760/255, 21590/255, + -19200/255, 31800/255). + |