[OpenJDK 2D-Dev]  Review request for 8023794: [macosx] LCD Rendering hints seems not working without FRACTIONALMETRICS=ON
andrew.brygin at oracle.com
Fri Mar 27 14:50:25 UTC 2015
There is a minor update in the fix: it does not worth to blend
and white-on-black glyphs for the case of AA glyphs, because it makes no
CGGlyphImages.m, lines 294 - 325, 755 - 763, and 787 - 794:
I have also modified the AntialiasDemo a bit in order to render the
sample text in different colors, and in order to render into a volatile
image as well:
It could be used to assess the change in glyph generation.
On 3/26/2015 3:59 PM, Andrew Brygin wrote:
> Hi Chris,
> thank you for the comments and explanation. I have updated the
> and comments in OGLTextRenderer.c accordingly:
> Good to know that you keep an eye on the OGL pipeline :)
> On 3/25/2015 8:24 PM, Chris Campbell wrote:
>> Hi Andrew,
>> That's a good find re: pow(). In the comment at lines 277-283 I
>> mentioned that there was only a scalar variant of pow(). I wonder if
>> that was a limitation in some early version of GLSL I was using or
>> perhaps some driver bug/restriction. According to all the docs I can
>> find the vector variants have been there all along:
>> So now I'm wondering if the slowness was actually due to me trying 3
>> scalar pow() calls versus one vector pow() call.
>> Oh, aha! I think this explains part of it:
>> 269 * This is the GLSL fragment shader source code for rendering
>> 270 * text. Do not be frightened; it is much easier to understand
>> than the
>> 271 * equivalent ASM-like fragment program!
>> Looks like I wrote the original version of this shader using the
>> GL_ARB_fragment_program language, which indeed only had a scalar POW
>> instruction (see section 126.96.36.199):
>> And then I'm guessing that when I rewrote it in more modern GLSL, I
>> didn't notice that pow() supported vectors. Sigh. That 3D texture
>> LUT was a lot of work for a whole lot of nothing.
>> In any case, you might want to rewrite the comment at lines 277-283
>> to suit the new code. Same goes for the comment at line 315:
>> // gamma adjust the dest color using the invgamma LUT
>> Also, I noticed that the restrictions in
>> OGLContext_IsLCDShaderSupportAvailable() could be loosened since you
>> only need 2 texture units now. Just in the extremely unlikely case
>> that anyone's running this stuff on ancient hardware :)
>> Andrew Brygin wrote:
>>> Hello Phil,
>>> could you please take a look to updated version of the fix?
>>> * OGLTextRenderer.c
>>> It was discovered, that in some cases lcd glyphs had visible 'dark
>>> border' around.
>>> This border appeared due to the gamma correction in lcd shader, which
>>> uses lookup
>>> on 3D texture instead of using 'pow' routine. The texture is populated
>>> with significant
>>> granularity (16 points per edge), what is a root cause of rough
>>> interpolation of color values.
>>> Suggested change is to eliminate the interpolation and use 'pow'
>>> It gives more accurate color values, and does not introduce significant
>>> performance hit
>>> (see benchmark summary below).
>>> However, this part of the fix affects not only macosx, but any platform
>>> where OGL text
>>> shader can be used, so it probably worth to split into a separate fix.
>>> Number of tests: 4
>>> Overall average: 42.68027553311743
>>> Best spread: 3.49% variance
>>> Worst spread: 29.59% variance
>>> (Basis for results comparison)
>>> Number of tests: 4
>>> Overall average: 42.468941501367084
>>> Best spread: 2.51% variance
>>> Worst spread: 29.44% variance
>>> Comparison to basis:
>>> Best result: 103.28% of basis
>>> Worst result: 97.36% of basis
>>> Number of wins: 1
>>> Number of ties: 2
>>> Number of losses: 1
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