A situation with some mid-coloured pixels

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William
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A situation with some mid-coloured pixels

Post by William » Fri Mar 30, 2012 2:57 pm

Some readers may have already noticed the following graphic in the Gallery thread about my Sonnet Calligraphic font.
starry_night_with_snow.png
starry_night_with_snow.png (8.92 KiB) Viewed 2629 times
As part of my evaluation of the graphic prior to uploading it to the forum, I had a look at the graphic in Microsoft Paint, including using the 8x magnification.

I noticed something that seemed strange to me, yet, as the image seems, to my eyes at least, to look good at 1x magnification I proceeded to use it.

What seems strange is an effect that seems to appear throughout the graphic.

Please consider the main vertical part of the letter i of the image at 8x magnification in Microsoft Paint.

If one looks at the glyph for the i in the font using FontCreator, the vertical of the i is 64 font units wide, going from an x position of 64 pixels to an x position of 128 font units, with the glyph having an advance width of 128 font units, and by my calculations should display at precisely 3 pixels wide in the graphic, with 3 pixels of background to its left. This is because 72 points will be displayed as 96 pixels in a Windows display and for this font 2048 font units is thus 96 pixels at 72 point, so 64 font units will display as 3 pixels: that is, 96 times (64 divided by 2048) pixels.

Using the Pencil tool of Microsoft Paint with red ink on top of a copy of the graphic display at 8x magnification shows that this calculation of 3 pixels is correct.

What puzzles me is as to why all of the pixels of the vertical of the i are not pure white with all of the pixels of the gaps each side of that vertical all being the same dark blue colour.

This type of effect seems to happen with many of the verticals of the letters. The left side is always crisp, yet the right side often has a mid-coloured pixel. The letter w has multiple effects.

I note that the upper and lower ends of the vertical of the letter i are displayed crisply. The effect that is puzzling me seems to be an effect along the horizontal direction only.

I am wondering if this is an effect of something in the font or something that is happening as an effect of the PagePlus X4 program - maybe it is something being done automatically by PagePlus X4 to improve the look of the result.

Anyway, I am puzzled by this effect and wonder if anyone can throw any light on what is happening please.

William Overington

30 March 2012

Bhikkhu Pesala
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Re: A situation with some mid-coloured pixels

Post by Bhikkhu Pesala » Fri Mar 30, 2012 7:01 pm

Maybe something to do with your Windows Cleartype settings, or perhaps greyscale rendering in the font. I presume that your fonts are unhinted.
My FontsReviews: MainTypeFont CreatorHelpFC12 Pro + MT9.0 @ Win10 1903 build 18362.356

William
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Re: A situation with some mid-coloured pixels

Post by William » Sat Mar 31, 2012 8:29 am

Bhikkhu Pesala wrote:Maybe something to do with your Windows Cleartype settings, or perhaps greyscale rendering in the font. I presume that your fonts are unhinted.
Thank you for your reply.

Yes, my fonts are unhinted, though in most of my fonts, including Sonnet Calligraphic, I do try to help the rendering system by having verticals on lines that I calculate will be where pixel edges will occur at multiples of 12 point sizes, such as 24 point, 36 point and so on. Some fonts then do not come out well on screen at 14 point and other intermediate sizes.

I found the place within the Windows Control Panel where the choice of font smoothing method is controlled. The dialogue panel offered the choice of having font smoothing or not, controlled by a checkbox, and then if smoothing is on, having Standard or Cleartype.

Font smoothing was on, set as Standard.

I tried turning the smoothing off and produced the following graphic. (I turned it back on afterwards).
Studying it in Microsoft Paint the effect that I described before seems to be still there.
starry_night_with_snow_unsmoothed.png
starry_night_with_snow_unsmoothed.png (8.92 KiB) Viewed 2618 times
I looked at the Sonnet Calligraphic 039 font in FontCreator 5.6 using Format Grayscale... and it has the following for Grayscale.

Gridfitting is unchecked. Grayscale rendering is checked.

Under Gasp ranges there is one line of data.
Limit Flags
65535 Grayscale Rendering

At the time of writing, I do not understand the significance of Grayscale rendering being checked and that data being in the Gasp ranges section.

So I made a test font, Sonnet Calligraphic 939 that is the same as Sonnet Calligraphic 039 except that the Grayscale rendering checkbox has been unchecked and a few other differences due soley to changing the name and the date of the font.

I then produced the following graphic, which when studied in Microsoft Paint did not have the effects described eariler for the original image.
starry_night_with_snow_939.png
starry_night_with_snow_939.png (4.55 KiB) Viewed 2618 times
starry_night_with_snow.png
starry_night_with_snow.png (8.92 KiB) Viewed 2618 times

The original image is repeated for ease of comparison of the two images together.

Here is the test font.
SONNC939.TTF
Sonnet Calligraphic 939 font, a test version of the Sonnet Calligraphic 039 font with the Grayscale rendering checkbox unchecked.
(44.7 KiB) Downloaded 228 times
Thank you again.

William Overington

31 March 2012

William
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Re: A situation with some mid-coloured pixels

Post by William » Sat Mar 31, 2012 12:44 pm

Some further notes on the images starry_night_with_snow.png and starry_night_with_snow_939.png.

The file starry_night_with_snow.png has a larger file size than the file starry_night_with_snow_939.png.

The image in starry_night_with_snow.png has sixteen colours of pixels whereas the image in starry_night_with_snow_939.png has two colours of pixels.

William Overington

31 March 2012

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