-------- Original Message --------
Subject: Re: pix buf and colormaps
Date: Thu, 28 Jun 2012 15:14:27 +0200
From: Kees Kling <[email protected]>
To: Kjell Ahlstedt <[email protected]>
On 06/27/2012 04:26 PM, Kjell Ahlstedt wrote:
2012-06-26 11:44, Kees Kling skrev:
Hi,
I have created a pix_buf from 8 bits data with the function
create_from_data
<http://developer.gnome.org/gtkmm/stable/classGdk_1_1Pixbuf.html#a8a3b524f26acd2f9efc4abe9c294d341>
(const guint8* data, Colorspace
<http://developer.gnome.org/gtkmm/stable/group__gdkmmEnums.html#ga866d716154abb7f5be26bd36b3017d3f>
colorspace, bool has_alpha, int bits_per_sample, int width, int
height, int rowstride).
It displays fine, but only in greyscale, so I must attach a
colortable, which maps a 8 bits value to an RGB color and preferable
to an RGBA color. What the best way to do this, I can't find much
documentation.
Regards
Kees Kling
The documentation of the C module gdk-pixbuf is located at
http://developer.gnome.org/gdk-pixbuf/stable/.
Perhaps you can find some information there, e.g. in "The GdkPixbuf
Structure" section at
http://developer.gnome.org/gdk-pixbuf/stable/gdk-pixbuf-The-GdkPixbuf-Structure.html.
When I look at that documentation and a small part of the gdk-pixbuf
source code, I get the impression that each pixel is represented by 3
or 4 bytes, called either channels or samples: one byte each for red,
green, blue, and an optional byte for an alpha channel. But if that's
the whole truth, I don't understand why you get only greyscale pictures.
Kjell
Hi Kjell,
my data is just one byte and I want to display it as a color image. So
for that I'm going to use a colortable with 255 entrys and in fact I
have to translate every byte value in 3 or 4 bytes found in the
colortable. It is nothing new, because I think bmp format does the same.
Off coarse it is possible to do just a one by one pixel translation, but
my data could be rather big, so there is a time and mem penalty. I
should like to know if there is a better way
Regards
Kees
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