[sane-devel] Does sane_read return multiple scanlines?

Henning Meier-Geinitz henning@meier-geinitz.de
Wed, 30 Apr 2003 11:27:29 +0200


On Tue, Apr 29, 2003 at 05:32:27PM -0500, Peter Chen wrote:
> I am a little confused about this. I guess sane_read could return multiple
> scanlines, the number of bytes returned is in len. 

That's true. sane_read is independent from scan lines. It can return
only one byte (or 0 in non-blocking mode) and upto maxlen bytes. That
can be part of a scan line or multiple scan lines.

> The width of the image is
> in parm.pixels_per_line, the height of the image is in parm.lines,
> parm.bytes_per_line could be the same as parm.pixels_per_line or
> parm.pixels_per_line*3, is this correct?

Basically, yes. bytes_per_line is something like pixes_per_line *

To be exact, bytes_per_line can be bigger than pixels_per_line *
bytes_per_pixel. But I'm not sure if any frontends supports this
feature for anything other than lineart mode.