interactive frequency filtering program geoff franz
TRANSCRIPT
Interactive Frequency Filtering Program
Geoff Franz
Overview
Concept and Problem Statement Solution User’s Guide Program Components Suggestions for Future Revisions Demo
Concept and Problem Statement
Sometimes you find images that suffer from obvious frequency-domain artifacts (e.g., halftoning, banding, etc)
I don’t know of any programs that let someone interactively filter in the frequency domain and see the results in real time
Solution
Write my own!
User’s Guide – Startup Screen
This is what the user sees when the program is launched.
User’s Guide – Opening an Image
This is what the user sees when a large image is opened.
User’s Guide – Opening an Image
This is what the user sees when a small image is opened.
User’s Guide – Drawing the Mask
The white lines are what the user sees when drawing with a small brush.
User’s Guide – Drawing the Mask
The white lines are what the user sees when drawing with a large brush.
User’s Guide – Drawing the Mask
The black areas are the result of drawing the mask.
User’s Guide – Mask Smoothing
The program can also create smoothed masked areas.
User’s Guide – Final Result
This is an example of a possible end result.
Program Components
These are the procedures and functions I wrote to solve the problem
Gaus, Show_FFT, Image_Display, Drawline_Draw_Events, Wid_Base_0_Event, IFF_GUI
Info structure They are explained in the following slides
Gaus
Returns a Gaussian function given an input.
Equation:
The Gaus function has obvious applications outside of this program, although it’s been written many times before
2xe
Show_FFT
Prepares a shifted FFT array for displayZeroes out the DC componentApplies an overall logarithmic brightness
transformApplies a radially-dependent brightness
transform Displays the modified FFT in the chosen
window
Image_Display
Reads in an image Computes the FFT and creates a mask Initializes an “info” structure that is used for the
remainder of the program Displays the image in the left and right panels,
and calls Show_FFT to display the FFT in the center panel
Enables button events in the center draw widget
Info Structure info = {image:image, $ ;the image itself pixID:-1, $ ;window ID of the hidden pix map fftimage:fftimage,$ ;FFT of the image wid0:wid0, wid1:wid1, wid2:wid2, $ ; window IDs imageID:WID_DRAW_0,$ ;left draw widget ID drawID:WID_DRAW_1,$ ;center draw widget ID filtID:WID_DRAW_2, $ ;right draw widget ID xsize:xs, ysize:ys, $ ;dimensions of the image xstart:-1, ystart:-1,$ ;starting location of the drawn line mask:mask, $ ;mask for the FFT xmid:xmid, ymid:ymid, $ ;central pixel location xvalues:ptr_new(),yvalues:ptr_new(),$ ;vertices for drawing the line buttonUsed:'None', $ ;which mouse button is currently selected ;this could be used to enable different ;functionality from the right mouse button drawColor:!D.N_colors-1} ;set the draw color to white
Drawline_Draw_Events
Loosely based on David Fanning’s drawline.pro example
This code handles all mouse events in the center draw widget
Uses the IDL PlotS procedure to draw the lines on the screen
Reads the slider to determine brush thickness Modifies the mask and updates the screen
Wid_Base_0_Event
Handles all other events (buttons and slider)
The following code is contained within this procedure:Testing if an image is valid before openingSaving the filtered image Smoothing the maskRevert back to the original state
IFF_GUI
This is where the widgets are created. Not too exciting.
Suggestions for Future Revisions
All of my suggestions fall into one of three categories:
Robustness and bug fixes Features (low-hanging fruit) Aesthetics
Suggestions: Robustness
Properly handle TIFF, PNG, GIF, and color images of all kinds
Fix the bug where if the user clicks outside the draw widget, drags the mouse inside, and releases, the program crashes when it tries to dereference a null pointer
Fix the bug where it crashes if a user clicks on a button (other than open image) before an image is loaded
Suggestions: Features
Undo last line drawn button Display color images and work on the
channels individually Add the ability to draw boxes and circles Add the ability to save to different file
formats other than PNG
Suggestions: Aesthetics
Make the GUI shrink to accommodate smaller images, so less space is wasted
Demo
The following is a demonstration of my program