HW2, Computer problem, Part (a)
EECS 203A, Digital Image Processing. UCI. Fall 2004
Nasser Abbasi


Define the transformation and generate 2 lookup tables and plot the curves. I also list the first and last 5 rows in each table for each curve to better see the values. The first column in the table is the r values and the second column is the s values.

In[27]:=

... 2371;, RowBox[{RowBox[{tbl2, =, RowBox[{process, [, RowBox[{1., ,, 1.5}], ]}]}], ;}], }]}]

0 0
1 6
2 10
3 13
4 16

...\n 251 252 252 253 253 254 254 254 255 255

[Graphics:HTMLFiles/index_3.gif]

lookup table has size= {256, 2}

0 0
1 0
2 0
3 0
4 1

...\n 251 249 252 251 253 252 254 254 255 255

[Graphics:HTMLFiles/index_6.gif]

Now set current directory to where the image is (same folder as this note book) and read the image file

In[34]:=

SetDirectory[ToFileName[Extract["FileName"/.NotebookInformation[EvaluationNotebook[] ... ; rows = 480 ; cols = 640 ; data = FastBinaryFiles`ReadListBinary[fileName, Byte] ;   

Now that the image is read into data, we display it before appying GLT on it.
    

In[39]:=

ListDensityPlot[Reverse[Partition[data, cols]], MeshFalse, FrameFalse, ImageSize {rows, cols}, PlotRangeAll, AspectRatioAutomatic] ;

[Graphics:HTMLFiles/index_9.gif]

Now apply first GLT to this image.c=1.0,γ=0.67 and display the result

In[40]:=

out = applyGLT[Flatten[data], tbl1] ; fileName = "cat_low_gamma.raw" ... [fileName] ; FastBinaryFiles`WriteBinary[strm, Flatten[out], Byte] ; Close[strm] ;

[Graphics:HTMLFiles/index_11.gif]

Now apply second GLT to this image.c=1.0,γ=1.5 and display the result

In[45]:=

out = applyGLT[Flatten[data], tbl2] ; fileName = "cat_high_gamma.raw" ; strm = FastB ... OpenWriteBinary[fileName] ; FastBinaryFiles`WriteBinary[strm, Flatten[out], Byte] ; Close[strm] ;

[Graphics:HTMLFiles/index_14.gif]

Conclusion

With γ=1.5,the new image is darker than the original image.With γ=0.67,the new image is lighter than the original image.Looking at the curves we see that with smaller γ darker areas are spread more over to the lighter gray level,and the reverse happens with higher γ

Created by Mathematica  (October 19, 2004)