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haochen

Member

From: Berlin

Registered: 2015-03-01

Posts: 1

Distorted image in jfbview and fbgrab

I'm using X-less Arch on Acer AO751h (poulsbo machine).

When I read PDF with jfbview, and take a screenshot with fbgrab, the result is always distorted.
Then I notice the reason from the output of "fbgraph -v test.png":

frame buffer fixed info:
id: "psbdrmfb"
type: packed pixels
line length: 8192 bytes (2048 pixels)

frame buffer variable info:
resolution: 1366x768
virtual resolution: 1366x768
offset: 0x0
bits_per_pixel: 32
grayscale: false
red:   offset: 16, length: 8, msb_right: 0
blue:  offset: 0, length: 8, msb_right: 0
green: offset: 8, length: 8, msb_right: 0
alpha: offset: 0, length: 0, msb_right: 0
pixel format: standard
Resolution: 1366x768 depth 32
Converting image from 32
Now writing PNG file (compression -1)

So each line is 2048 pixels long, while my screen is 1366 pixels wide.  I guess my screen only shows part of the whole picture.  But when fbgrab takes a screenshot, it reads 1366 pixels for a row, and continues for the next 1366 pixels in the same line.  This produces a distorted screenshot.  I verified this theory by running "fbgrab -v -w 2048", the result is nice but wider, of course.

So how can I configure the "line length" of psbdrmfb to be compatible with my resolution?  Or is it a bug of fbgrab and jfbview? afterall, fbpdf works perfectly.

In /etc/default/grub, I have

 GRUB_CMDLINE_LINUX_DEFAULT="quiet psbdrmfb fbcon=scrollback:512K" 

and

 GUB_GFXPAYLOAD_LINUX=1366x768x32 

and in /etc/mkinitcpio.conf, I have

 MODULES="gma500_gfx" 

Last edited by haochen (2015-03-01 22:04:18)