LDR Tonemapping
by Nasca
Octavian PAUL
Introduction
This
program is for tonemapping the low-dinamic-range images. Unlike the
other tonemappers, this takes 1 LDR image and outputs another LDR
image. This reduces the global contrast of the pictures and increases
the local contrast.
Features
-
There
are two tonemapping algorithms: one is very fast and the other is very
precise
-
The
user has full control on many parameters of the tonemapping algorithm
-
Instant
preview is available, and there is support for splitting the screen
into the original/processed image
-
The
program includes batch processing mode
-
Thanks
to the FreeImage
library, it supports many image formats
-
It
runs on Linux and Windows
-
It
is a Free Software, released under GNU General Public License
Examples and screenshots
Click on image below to see more screenshot
and some examples:
Download
You can download the source code for
Linux or binary for Windows from HERE.
Usage
This tonemapper produces a desatured and blured version of the image
which is combine with each RGB channel using a function. This process
can be applied more than one time and each time the effect is applied
is called a 'stage'. After this, the user can desaturate the portions
of the image where the initial value was either very low or very high.
After this step, there is an optional unsharp mask to enhance the
details of the processed image.
The user can
view the original image, the processed image or both images same time
(original is in the left and processed in the right).
User can pan the image by dragging with the mouse and can zoom by using the scroll wheel.
Tonemapping parameters
Usually,
the parameters are not linear: on lower settings they grow very slow,
but on the higher settings they grows very fast. This produces more
'natural' behaving settings.For each stage this parameters are
available:
- enabled - if the current tonemapping stage is enabled
- power - how strong the effect is applied
- blur - how strong the image is blured before combining with
the original image with the tonemapping function
The next parameters are global for the whole effect:
- function
- this is the function which combines the original RGB chanels with the
desaturated blured image. This function used on each of the tonemapping
stage. It can linear or power. Basicaly, these function increase the
value where both the original and blurred image's value are low and do
the opposite on high values
- stretch contrast - this stretch the contrast of the
original image. This is applied before the tonemapping process
- high saturation and
low saturation - Usually the (perceived) saturation is increased. The
user can choose to lower the saturation on original highlight and
shadows from the image with these parameters
- fast mode - there
are available two ways to do the tonemapping: using a very fast
algorithm, which might produce artifacts on the image or a more precise
algorithm, which is slower
Unsharp parameters
- U.M. enabled - enable the unsharp mask filter
- U.M. power - the strenght of the unsharp mask
- U.M. blur - how much the image is blurred into the unsharp
mask filter
- U.M. threshold - this avoids increasing the noise of the
unsharp mask filter
View
- preview - if checked the processed image is shown, else the
original image is displayed
- histogram - shows the histogram of the displayed image
- show - "image" - show one image';
"half" shows the original image in the left and the processed in the
right. The next two modes f(x) and f(x,y) shows the tonemapping
function and is more used in developing this program; "x" here
represents the original channel value and "y" represents the value of
the blurred image. f(x) shows the function as a line for every possible
input values, the other parameter (blurred, or 'y') is set by clicking
of the mouse on the screen. The f(x,y) mode shows the function for
every possible combination of input channel value and 'blurred' value.
Menus
File menu
- Open image... - open an image from file. You can load
many file types, if you check to show all files.
- Save image... - saves the processed image to the file
- Batch
process images... - select many files from a directory and select the
output directory. After this, all images are processed with the current
setting. This is very useful to process a time-lapse sequence of
images.
- Reset parameters - all tonemapping parameters are set to
default
- Open parameters... - loads the tonemapping parameters
from a file
- Save parameters... - write the current parameters to a
file
- Exit - close the program
Help menu
- About... - show the copyright info
ToDo
History
20090121
First public release
20090201 Added preview on file open, zoom by mouse scroll wheel
Contact:
zynaddsubfx AT YAHOO DOT COM