DPI-aware NSIS

[p0nce]

When using ManifestDPIAware true in NSIS script, the image given to MUI_HEADERIMAGE_BITMAP doesn't display right, whatever the DPI.

• 150% DPI

  

• 100% DPI

  

[p0nce]

Lots of good practice there: https://github.com/notepad-plus-plus/notepad-plus-plus/blob/2768cf5422e6a443e7ed043ddd21a961e5c9859d/PowerEditor/installer/nppSetup.nsi#L30

[p0nce]

OK so the BMP that comes with NSIS doesn't exhibit this wrong behaviour! (EDIT: yes it does) There is something interesting inside. nsis3-vintage.zip

Comparison of that BMP when re-saved with MSPaint, colors are then wrong, which could create the impression of bad resampling.

[p0nce]

Comparison of bitmap header in NSIS and MSPaint output:

• same size, same BMP type
• BI_RGB as biCompression
• bitness = 8
• "right" BMP has a biSizeImage of 2 bytes more
• identical biXPelsPerMeter and biYPelsPerMeter
• "wrong" BMP has no palette

[p0nce]

Learning after a good deal of investigation:

• There is no way to improve the resampling apparently in case of 150% DPI. Even NSIS bitmaps suffer. The workaround would probably to adopt a "pixel" style.

• that image resampling is not worse than blurry text anyway, and only shows in non-100% DPI.

• BMP needs to be saved either in MSPaint, or in GIMP with the export option "do not add colorspace information". It can then be: 8-bit indexed or 24-bit true color. More tests needed. No way to have alpha.

• [x] Update documentation about that MSPaint export, we now know an alternative for it

• [x] Set ManifestDpiAware to true in generated NSIS script

• [x] Update Auburn image for the installers to support such a nearest-neighbour resize

[p0nce]

Done.