The imagefont file is an image file in a format that LÖVE can load. It can contain transparent pixels, so a PNG file is preferable, and it also needs to contain spacer color that will separate the different font glyphs.
The upper left pixel of the image file is always taken to be the spacer color. All columns that have this color as their uppermost pixel are interpreted as separators of font glyphs. The areas between these separators are interpreted as the actual font glyphs.
It is possible to have more areas in the image than are required for the font in the love.graphics.newImageFont() call. The extra areas are ignored.
In versions prior to 0.10.0 the width of the separator area after a particular font glyph sets the amount of space that goes after the glyph. As of 0.10.0, it is possible to add negative spacing for all characters by using the 3-parameter version of love.graphics.newImageFont and giving a negative number as the third parameter.
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