vbaderks / netpbm-wic-codec

Experimental C++ Windows Imaging Component (WIC) for Netpbm (.pgm) files

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netpbm-wic-codec's Issues

'qualified' winrt in line 8 of pnm_header_test.cpp?

netpbm-wic-codec/test/pnm_header_test.cpp

Line 8 in 38bce14

import winrt;

maybe it would be better to write here

import test.winrt;

instead of just

import winrt;

ppm is not sRGB

I think the toplevel README would at least reference the original intend of the ppm file format specification:

• https://netpbm.sourceforge.net/doc/ppm.html

In the raster, the sample values are "nonlinear." They are proportional to the intensity of the ITU-R Recommendation BT.709 red, green, and blue in the pixel, adjusted by the BT.709 gamma transfer function. (That transfer function specifies a gamma number of 2.2 and has a linear section for small intensities). A value of Maxval for all three samples represents 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).

BT.709's range of channel values (16-240) is irrelevant to PPM.

ITU-R Recommendation BT.709 is a renaming of the former CCIR Recommendation 709. When CCIR was absorbed into its parent organization, the ITU, ca. 2000, the standard was renamed. This document once referred to the standard as CIE Rec. 709, but it isn't clear now that CIE ever sponsored such a standard.

Note that another popular color space is the newer sRGB. A common variation from PPM is to substitute this color space for the one specified. You can use pnmgamma to convert between this variation and true PPM.

Note that a common variation from the PPM format is to have the sample values be "linear," i.e. as specified above except without the gamma adjustment. pnmgamma takes such a PPM variant as input and produces a true PPM as output.

the use of the 'WINRT_NO_MAKE_DETECTION' define in the project

Is it absolutely necessary to mark implementation classes of this project 'final'? When doing so, you need to define the symbol 'WINRT_NO_MAKE_DETECTION', and the documentation strongly recommends to not define this symbol (https://learn.microsoft.com/en-us/windows/uwp/cpp-and-winrt-apis/macros#winrt_no_make_detection). The other document (https://learn.microsoft.com/en-us/windows/uwp/cpp-and-winrt-apis/diag-direct-alloc#the-solution-with-cwinrt-20) explains that there is no need to mark the whole implementation class 'final', as the instantiated type will always be final. Again, any virtual functions in your implementation can be marked as final, if need be. So, if it is possible to avoid marking the whole classes as final, the project would conform to the documentation recommendation against the 'WINRT_NO_MAKE_DETECTION' define.