[ft] need help with freetype + xlib.

[Yves Daoust]

To summarize, if I may: for an RGBA image having Height rows, each Width
pixels wide,

	Pitch = 4 x Width + Pad		(4 x 8 + 0 = 32 bytes per row)
	Size = Pitch x Height		(32 x 16 = 512 bytes per image)

-----Original Message-----
From: freetype-bounces+yves.daoust=visionforvision.eu at nongnu.org
[mailto:freetype-bounces+yves.daoust=visionforvision.eu at nongnu.org] On
Behalf Of Glynn Clements
Sent: Tuesday, June 18, 2013 7:21 PM
To: First Last
Cc: xorg at lists.x.org; freetype at nongnu.org
Subject: Re: [ft] need help with freetype + xlib.


First Last wrote:

> Hi, I try to use freetype with xlib, I , I need to pass a char type 
> array (RGBA/pixel) to a xlib function.
> 
> from freetype I got :
> 
>   face->glyph->bitmap.pixel_mode = 2
> so if I understood corectly in face->glyph->bitmap.buffer datas are stored
in gray level.
>   face->glyph->bitmap.rows=16
>   face->glyph->bitmap.width=8
>   face->glyph->bitmap.pitch=8
> 
> so I guess,  length of face->glyph->bitmap.buffer = 1(gray 
> lvl)*16(width)*8(rows)=128 unsigned chars, right ?

Right answer, wrong reasoning; width should be replaced by pitch. The two
values may differ if there is padding between lines.

> then I create an array of char for xlib from 
> face->glyph->bitmap.buffer
> 
>   for(i=0;i<128;i++){
>     Xdata[4*i]     = face->glyph->bitmap.buffer[i];
>     Xdata[4*i+1] = face->glyph->bitmap.buffer[i];
>     Xdata[4*i+2] = face->glyph->bitmap.buffer[i];
>     Xdata[4*i+3] = 255;
>    } and I try to create a XImage :
>   ximage = XCreateImage(display, DefaultVisual(display,0), 24, 
> ZPixmap, 0,
>                                         &Xdata[0], 8/*rows*/, 
> 16/*width*/, 32/*RGBA*/, 8/*pitch??*/);


The last argument (bytes_per_line) should be 32 (8 pixels wide at 4 bytes
per pixel).

--
Glynn Clements <glynn at gclements.plus.com>

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