Yes, the only difference in blending is that subpixel mode does it 3 times per pixel.
The filter is color-balanced, but not normalized. Values above 0x100 will have to be clamped and this non-linearity causes distortion and adds to color fringing. Stem darkening is the better way to increase contrast. ________________________________________ From: [email protected] <[email protected]> on behalf of Nikolaus Waxweiler <[email protected]> Sent: Friday, November 20, 2015 10:08 AM To: [email protected] Subject: Re: [ft-devel] gamma correction demo images > I did not work on subpixel rendering in FreeType, but I assume it is > similar to what Adobe does. Here is a brief summary. I'm currently writing up the documentation for ftautoh.h, do I understand correctly that the steps for linear alpha blending and gamma correction of gray and subpixel-rendered glyphs are exactly the same? Meaning: 1. Take the foreground and background colors (e.g., in sRGB space) and apply gamma to get them in a linear space. 2. Blend the two linear colors using the alpha value from the glyph's coverage bitmap 3. Apply inverse gamma (e.g. 1.8) to the blended pixel and write it back to the image. > The density computed for each subpixel must be distributed equally to > all color channels. Werner, http://freetype.org/freetype2/docs/reference/ft2-lcd_filtering.html suggests [0x10, 0x50, 0x60, 0x50, 0x10] as a possible LCD filter to use when doing LAB+GC. Is this correct and does what Dave suggests here? The sum seems to go above 0x100? And if it is, would it make a good candidate for a new FT_LCD_FILTER_EQUAL_WEIGHT that LAB+GC-enabled libs can set? _______________________________________________ Freetype-devel mailing list [email protected] https://lists.nongnu.org/mailman/listinfo/freetype-devel _______________________________________________ Freetype-devel mailing list [email protected] https://lists.nongnu.org/mailman/listinfo/freetype-devel
