add function to support inserting custom color into IndexedColors Map

[deleteJ]

this closes #979

[tonyqus]

#699

[tonyqus]

The size of IndexedColor is fixed. We cannot simply add new custom color to indexed color list

https://github.com/ClosedXML/ClosedXML/wiki/Excel-Indexed-Colors

[tonyqus]

https://stackoverflow.com/questions/10528516/poi-setting-cell-background-to-a-custom-color

[deleteJ]

oh, i'll a take a look, thanks

[deleteJ]

questions:

1. why in IndexedColors we have some index not used(like 32-39)?
2. I should add API to allow uses to replace indexedColors on some index?

[Bykiev]

2. I should add API to allow uses to replace indexedColors on some index?

The API is already available:

npoi/main/HSSF/UserModel/HSSFPalette.cs

Line 121 in b4b94fe

public void SetColorAtIndex(short index, byte red, byte green, byte blue)

[Bykiev]

1. why in IndexedColors we have some index not used(like 32-39)?

These indexes are free and should be used for custom colors

[deleteJ]

Hi @Bykiev
thanks for your reply...

I'm quite new to this npoi project, here's some learnings

1. HSSFWorkBook can use getCustomPalette and SetColorAtIndex to use its own RGB color
2. XSSFWorkBook do not have such API, but only XSSFColor constructor

public XSSFColor(IndexedColors indexedColor)

but this requires color registed in class IndexedColors

public static IndexedColors ValueOf(int index)
{
    if(mappingIndex.ContainsKey(index))
        return mappingIndex[index];
    throw new ArgumentException("Illegal IndexedColor index: " + index);
}

3. This issue requests APIs to add new color on empty index
4. should we allow to replace existing default indexed colors, I prefer NO...

correct me if anything wrong, thanks

[tonyqus]

http://dmcritchie.mvps.org/excel/colors.htm

[deleteJ]

On POI side, they(IndexedColors) have index [0, 31], [40, 63], 56 colors supported

but out of these 56 colors, there are 9 colors which are duplicated, index [0, 7] and index 27 (LIGHT_TURQUOISE)
that's why in current NPOI indexedColors we don't have these indexes but actually they're same

[tonyqus]

Any update on this?