Skip to content
GitLab
Explore
Sign in
Primary navigation
Search or go to…
Project
U
uva
Manage
Activity
Members
Labels
Plan
Issues
Issue boards
Milestones
Wiki
Code
Merge requests
Repository
Branches
Commits
Tags
Repository graph
Compare revisions
Build
Pipelines
Jobs
Pipeline schedules
Artifacts
Deploy
Releases
Model registry
Operate
Environments
Monitor
Incidents
Analyze
Value stream analytics
Contributor analytics
CI/CD analytics
Repository analytics
Model experiments
Help
Help
Support
GitLab documentation
Compare GitLab plans
Community forum
Contribute to GitLab
Provide feedback
Keyboard shortcuts
?
Snippets
Groups
Projects
Show more breadcrumbs
Taddeüs Kroes
uva
Commits
eb66faab
Commit
eb66faab
authored
13 years ago
by
Sander Mathijs van Veen
Browse files
Options
Downloads
Patches
Plain Diff
ImProc: converted tabs to spaces and fixed some typo's.
parent
871fe57e
No related branches found
Branches containing commit
No related tags found
No related merge requests found
Changes
1
Hide whitespace changes
Inline
Side-by-side
Showing
1 changed file
improc/ass3/report/report.tex
+29
-28
29 additions, 28 deletions
improc/ass3/report/report.tex
with
29 additions
and
28 deletions
improc/ass3/report/report.tex
+
29
−
28
View file @
eb66faab
...
...
@@ -146,8 +146,8 @@ So, using the HSV color model does improve the results.
\subsection
{
Finding Waldo
}
The assignment is to find Waldo (
\emph
{
waldo.
png
}
) in a large image containing
Waldo and many other characters (
\emph
{
waldo
\_
env.
png
}
) using Histogram Backprojection.
The assignment is to find Waldo (
\emph
{
waldo.
tiff
}
) in a large image containing
Waldo and many other characters (
\emph
{
waldo
\_
env.
tiff
}
) using Histogram Backprojection.
The idea of Histogram Backprojection is explained in the paper by Swain and Ballard,
so we will not explain it here. The algorithm as described in the paper is as follows:
...
...
@@ -156,28 +156,29 @@ Given histograms $M$ (model, Waldo) and $I$ (environment), create the back proje
$
b
$
in the following steps:
\begin{enumerate}
\item
for each histogram bin
$
j
$
do
$
R
_
j :
=
frac
{
M
_
j
}{
I
_
j
}$
\item
for each
$
x, y
$
do
$
b
_{
x,y
}
:
=
min
(
R
_{
h
(
c
_{
x,y
}
)
}
,
1
)
$
\item
$
b :
=
D
^
r
*
b
$
\item
$
(
x
_
t, y
_
t
)
:
=
loc
(
max
_{
x,y
}
, b
_{
x,y
}
)
$
\item
for each histogram bin
$
j
$
do
$
R
_
j :
=
frac
{
M
_
j
}{
I
_
j
}$
\item
for each
$
x, y
$
do
$
b
_{
x,y
}
:
=
min
(
R
_{
h
(
c
_{
x,y
}
)
}
,
1
)
$
\item
$
b :
=
D
^
r
*
b
$
\item
$
(
x
_
t, y
_
t
)
:
=
loc
(
max
_{
x,y
}
, b
_{
x,y
}
)
$
\end{enumerate}
However, the assignment tells us to only implement steps 1-3.
\subsection
{
Mask
}
The algorithm is implemented in
\emph
{
back
\_
projection.py
}
. First, a mask is created
to ignore the white background in the
\emph
{
waldo.png
}
. This is needed because the
white color is not part of Waldo himself,. In fact, Waldo in the
\emph
{
waldo
\_
env.png
}
has a yellowish background behind him. The usage of a mask is simple: if the mask value
of a pixel is
\texttt
{
False
}
, the pixel's color is discarded in the creation of the
color histogram. The mask for Waldo is created by discarding all pixels with RGB
color (255, 255, 255), which has the following result:
\begin{figure}
[h]
\label
{
fig:mask
}
\includegraphics
{
mask.png
}
\caption
{
The mask used to ignore the white background in
\emph
{
waldo.png
}
.
}
The algorithm is implemented in
\emph
{
back
\_
projection.py
}
. First, a mask is
created to ignore the white background in the
\emph
{
waldo.tiff
}
. This is needed
because the white color is not part of Waldo himself. In fact, Waldo in the
\emph
{
waldo
\_
env.tiff
}
has a yellowish background behind him. The usage of a
mask is simple: if the mask value of a pixel is
\texttt
{
False
}
, the pixel's
color is discarded in the creation of the color histogram. The mask for Waldo
is created by discarding all pixels with RGB color (255, 255, 255), which has
the following result:
\begin{figure}
[H]
\label
{
fig:mask
}
\includegraphics
{
mask.png
}
\caption
{
The mask used to ignore the white background in
\emph
{
waldo.tiff
}
.
}
\end{figure}
\subsection
{
Basic algorithm
}
...
...
@@ -192,11 +193,11 @@ weight mask.
The following result is generated with 64 bins in each color dimension and a convolution
radius of 15 pixels:
\begin{figure}
[
h
]
\hspace
{
-4cm
}
\includegraphics
[width=20cm]
{
found
_
waldo.png
}
\caption
{
\emph
{
found
\_
waldo.
png
}
: Back projection of Waldo in the larger image, the
red spot is Waldo's location.
}
\begin{figure}
[
H
]
\hspace
{
-4cm
}
\includegraphics
[width=20cm]
{
found
_
waldo.png
}
\caption
{
\emph
{
found
\_
waldo.
tiff
}
: Back projection of Waldo in the larger image, the
red spot is Waldo's location.
}
\end{figure}
This result is created in roughly 27 seconds on a laptop from 2009.
...
...
@@ -217,11 +218,11 @@ that are further away from all other estimators than the diagonal of the model i
image is drawn over the larger image. With 32 bins in each color dimension, a threshold
of 0.25 and a convolution radius of 10 pixels, the result is as follows:
\begin{figure}
[
h
]
\hspace
{
-4cm
}
\includegraphics
[width=20cm]
{
k-means.png
}
\caption
{
\emph
{
k-means.png
}
: Multiple possible locations using a low threshold
and convolution radius.
}
\begin{figure}
[
H
]
\hspace
{
-4cm
}
\includegraphics
[width=20cm]
{
k-means.png
}
\caption
{
\emph
{
k-means.png
}
: Multiple possible locations using a low threshold
and convolution radius.
}
\end{figure}
\end{document}
...
...
This diff is collapsed.
Click to expand it.
Preview
0%
Loading
Try again
or
attach a new file
.
Cancel
You are about to add
0
people
to the discussion. Proceed with caution.
Finish editing this message first!
Save comment
Cancel
Please
register
or
sign in
to comment