You might want to try and disable MagickNET.OpenCL, that is the only thing that could affect the Quality. You will probably get a better result without it. And the Quality property for PNG does not work how you think it does. Here is an explanation:
And an answer to your other question are:
1: That is correct but that only works if your source image also has a color profile. In the next version of Magick.NET I have added the following new method to make this easier:
2: You can use image.GetAttribute("icc:description") for this but I will try to see if I can add this to the color profile class.
/* Untangle the "-quality" setting:
Undefined is 0; the default is used.
Default is 75
10's digit:
0 or omitted: Use Z_HUFFMAN_ONLY strategy with the
zlib default compression level
1-9: the zlib compression level
1's digit:
0-4: the PNG filter method
5: libpng adaptive filtering if compression level > 5
libpng filter type "none" if compression level <= 5
or if image is grayscale or palette
6: libpng adaptive filtering
7: "LOCO" filtering (intrapixel differing) if writing
a MNG, otherwise "none". Did not work in IM-6.7.0-9
and earlier because of a missing "else".
8: Z_RLE strategy (or Z_HUFFMAN_ONLY if quality < 10), adaptive
filtering. Unused prior to IM-6.7.0-10, was same as 6
9: Z_RLE strategy (or Z_HUFFMAN_ONLY if quality < 10), no PNG filters
Unused prior to IM-6.7.0-10, was same as 6
Note that using the -quality option, not all combinations of
PNG filter type, zlib compression level, and zlib compression
strategy are possible. This will be addressed soon in a
release that accomodates "-define png:compression-strategy", etc.
*/1: That is correct but that only works if your source image also has a color profile. In the next version of Magick.NET I have added the following new method to make this easier:
///<summary>/// Transforms the image from the colorspace of the source profile to the target profile. The/// source profile will only be used if the image does not contain a color profile. Nothing/// will happen if the source profile has a different colorspace then that of the image.///</summary>///<param name="source">The source color profile.</param>///<param name="target">The target color profile</param>publicvoid TransformColorSpace(ColorProfile source, ColorProfile target)