Re: [ft-devel] optimal configuration to render fonts using gamma correction
Hi all, I'm sorry I've disturbed this ML with my unclear questions. I did found out by myself how to have optimal font rendering. What I was missing was vertical font hinting because I was freely translating the y coordinate by fractional amount so that vertical hinting was actually lost. I understood now that vertical hinting is *very* important to have good looking fonts. Otherwise other important things I found out to have optimal rendering are: - antialising (of course) with subpixel rendering (very important) = the gamma value is less important but it seems to me that a gamma of 1.5 is a very good comprimise. You can also completely drop gamma correction and still it goods fine. - you can turn FT_LOAD_FORCE_AUTOHINTING since freetype autohinting seems to give excellent results - optionally activate FT_LOAD_TARGET_LCD and FT_LOAD_TARGET_LIGHT but without this latter the hinting is may be better (found out about them looking in libXft source code) - disable the font hinting along the horizontal axis (achieved by doing a x100 scale transform along x before loading the glyph) - use font kerning with fractional positioning along x and without rounding of the coordinates With all these attentions the results turns out to be excellent on the par with the better font system I know of. I found also that the results are better that Windows's ClearType (at least on XP), this latter does have too much colored fringes for my taste. Here a sample of the results that I obtain: http://imagebin.org/223827 I hope this can be helpful for other people since it took me a lot of time to figure out all the details. Best regards, Francesco ___ Freetype-devel mailing list Freetype-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/freetype-devel
Re: [ft-devel] optimal configuration to render fonts using gamma correction
What do you mean by washed out? _What's_ washed out? Regardless of what curve your grey-levels use, white should be white, and black should be black, and fonts are mostly black and white Hi, I'm sorry I was not clear to express the problem. By washed out I meant that, like in image http://imagebin.org/222768 the text is too much clear. To make an objective comparison I have compared the same text rendered with google chrome on ubuntu and gsl shell. The image is here: http://imagebin.org/222920 The text rendered with chrome is clearly more dark, more crisp, while with my rendering pipeline the text is quite clear. This is probably normal with antialising and gamma correction since the pixel does not have a 100% coverage but the final results, even if correct, does look too much clear, washed out as I was saying before. I guess that google chrome does use libxft on linux to render text so probably it is a the level of libxft that the rendering pipeline is defined. I'm wondering if they are using gamma correction or not, if it is the hinting that make the difference or if they use other special methods to increase font crispness. Francesco ___ Freetype-devel mailing list Freetype-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/freetype-devel
Re: [ft-devel] optimal configuration to render fonts using gamma correction
On 07/31/2012 01:51 PM, Francesco Abbate wrote: I believe that gamma correction is necessary to render properly antialiased graphics but when I render the text with gamma correction it looks too much light, almost washed out. An extremely powerful way to evaluate whether your gamma is correct is to use fore / back colors of the same luminosity but different hue. Then if your gamma is correct, the blending edges should have the same luminosity as the fore / back colors. See for example: http://people.freedesktop.org/~sandmann/srgb.png BTW, I've observed the same behavior that you observed in GLyphy. behdad ___ Freetype-devel mailing list Freetype-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/freetype-devel
Re: [ft-devel] optimal configuration to render fonts using gamma correction
2012/7/31 Behdad Esfahbod beh...@behdad.org: On 07/31/2012 01:51 PM, Francesco Abbate wrote: An extremely powerful way to evaluate whether your gamma is correct is to use fore / back colors of the same luminosity but different hue. Then if your gamma is correct, the blending edges should have the same luminosity as the fore / back colors. See for example: http://people.freedesktop.org/~sandmann/srgb.png Very interesting indeed. I've made the test and it seems that my (AGG) gamma correction is done right. http://imagebin.org/222801 If I disable gamma correction and subpixel rendering the quality get clearly worst. So the problem is still standing about why fonts looks washed with gamma correction. More important too, what is the better method to render fonts ? Disable gamma corrections ? Francesco ___ Freetype-devel mailing list Freetype-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/freetype-devel
Re: [ft-devel] optimal configuration to render fonts using gamma correction
Francesco Abbate francesco@gmail.com writes: So the problem is still standing about why fonts looks washed with gamma correction. More important too, what is the better method to render fonts ? Disable gamma corrections ? What do you mean by washed out? _What's_ washed out? Regardless of what curve your grey-levels use, white should be white, and black should be black, and fonts are mostly black and white [I guess you want to do any blending in a linear space (non-gamma-corrected), but obviously whatever you hand off to the display system should be in whatever space the display system expects...] -miles -- We are all lying in the gutter, but some of us are looking at the stars. -Oscar Wilde ___ Freetype-devel mailing list Freetype-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/freetype-devel
Re: [ft-devel] optimal configuration to render fonts using gamma correction
I wrote earlier: [I guess you want to do any blending in a linear space ^ and interpolation too, of course! (non-gamma-corrected), but obviously whatever you hand off to the display system should be in whatever space the display system expects...] -- Apologize, v. To lay the foundation for a future offense. ___ Freetype-devel mailing list Freetype-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/freetype-devel
