Image processing

When entering the “Image processing“ window, the position (X,Y) and gray value (G) of the image pixel pointed by the mouse arrow are shown at the upper left of this dialogue window. The name of the current image memory is indicated on the upper left corner of the window.

Buttons

- Button Clr: pressing this button to changing display color as follows:
(A) When a 24-bit BMP color image is loaded (Red/Reco.1, Green/Reco.2, Blue/Mask-B), three display modes are available: (1) individual gray-scale image, (2) individual color image, and (3) overlapped color image.
(B) When images are loaded independently and “Reco.1” is shown in “Image processing” window, pressing Clr-button to turn Reco.1 into cyan color and Mask B is shown as a red background image.

- Button Grp: Pushed down for applying action indicted with “ ’ ” to every image in the loaded image group;

- Button Histo.: For opening the “histogram” window to show the gray value histogram of the image part in a selected frame. When no frame is selected, the histogram is for the whole image;

- Button Undo: For undoing or redoing the previous image processing step;

- Button Reset: For canceling all image processing steps and restoring the original image;

- Button TJ: Used with mouse functions or others;

- Button Zoom: Used with mouse functions or others;

- Button I: Used to switch images in PIV image memories;

- Button S: Used to save changes made in the image processing window;

- Buttons “< and “>”: See below.

Mouse functions

- Draw a frame to show the detail: A frame can be drawn in the window by pressing and holding down the left mouse and moving the mouse arrow. After the frame is drawn, bitmap buttons Zoom and “TJ” are shown in the window. The frame and buttons are cleared by pressing the “TJ” button. When pressing Zoom button, window “Detail” is opened to display the image in the selected frame.

- Display gray value distribution along x- and y-cuts: By Moving mouse arrow to a desired point and clicking the right mouse button, the gray value distributions along the x- and y-cuts across the selected point are shown on the screen, and they disappear when clicking the right mouse again.

Image group display

When a PIV recording group is loaded, buttons “<” and “>” and the edit box (below button “Reset”) are enabled. The number of the current image is shown in the edit box. The image shown in the window can be selected by pressing buttons “<” or “>” or inputting a number in the edit box. When pressing “<” or “>” button, the current recording/vector number is decreased or increased with a skip number determined in the start window. 

Menu group “File”

File \ Export image - Used to export currently image into a Windows Bitmap file;

File \ Close - Used to close the “Image processing” window.

Menu group “Edit – General operations”

Edit \ Image operation \ Subtraction’ - Used to subtract a selected image from the current image;

Edit \ Image operation \ Overlap’ + - Used to overlap the current image with a selected image by using the maximum gray value of the two;

Edit \ Image operation \ Overlap’ - - Used to overlap the current image with a selected image by using the minimum gray value of the two;

Edit \ Image operation \ Average’ - Used to add a selected image to the current image, then the gray value divided by 2;

Edit \ Image operation \ Copy - Used to duplicate the current image to replace a selected image;

Edit \ Pixel operation \ Linear transformation’ - Used to linearly transfer the gray value distribution of current image with given parameters;

Edit \ Pixel operation \ Threshold’ - Used to cut off the gray values below or over a selected threshold (see window “Gray value (Threshold)”) then normalizing the gray value distribution;

Edit \ Pixel operation \ Square ’ - Used to non-linearly increase the image contrast;

Edit \ Pixel operation \ Binary’ - Used to binarize the current image with a selected threshold (see window “Gray value (Threshold)”);

Edit \ Pixel operation \ Root ’ - Used to non-linearly decrease the image contrast;

Edit \ Filter operation \ Regional normaliz.’ - Used to normalize the gray value of each pixel with minimal and maximal gray value in the neighborhood of selected size;

Edit \ Filter operation \ Unsharp mask #1’ - Used to process the current image with unsharp mask filter of selected size, then normalizing the gray value distribution; 

Edit \ Filter operation \ Unsharp mask #2’ - Used to process the current image with unsharp mask filter of selected size and cutting off the negative values;

Edit \ Filter operation \ Smooth filter’ - Used to process the current image with smooth filter of selected size; 

Edit \ Filter operation \ Median filter’ - Used to process the current image with median filter of selected size; 

Edit \ Filter operation \ Tracer filter’ - Used to filter both low and high frequency noises to make particle images of selected size more clear;

Edit \ Filter operation \ Expansion’ - Used to replace the gray value of each pixel with maximum in its 3x3-pixel neighborhood; 

Edit \ Filter operation \ MPIV filter’ - Used to reduce both high and low frequency noises in micro scale PIV recordings;

Edit \ Filter operation \ Erosion’ - Used to replace the gray value of each pixel with minimum in its 3x3-pixel neighborhood; 

Edit \ Image group \ Image group files \ Show histogram \ Selected frames - Used to display the histogram of selected image frames;

Edit \ Image group \ Image group files \ Show histogram \ 2nd exposures - Used to display the histogram of the 2nd exposures of selected PIV image pairs;

Edit \ Image group \ Image group files \ Show histogram \ 1st exposures - Used to display the histogram of the 1st exposures of

selected PIV image pairs;

Edit \ Image group \ Image group files \ Show file name - Used to display file name of current PIV recording, when a group of PIV recordings is loaded;

Edit \ Image group \ Image group files \  Save image - Used to save changes of current PIV recording into its original file, when a group of PIV recordings is loaded;

Edit \ Image group \ Image separation \ x-cut \ 1/2 - Used to separate vertical double images in the image group into single images with order of top first;

Edit \ Image group \ Image separation \ x-cut \ 2/1 - Used to separate vertical double images in the image group into single images with order of bottom first;

Edit \ Image group \ Image separation \ y-cut \ A-B - Used to separate horizontal double images in the image group into single images with order of left first;

Edit \ Image group \ Image separation \ y-cut \ B-A - Used to separate horizontal double images in the image group into single images with order of right first;

Edit \ Image group \ Image separation \ Video - Used to separate interlaced PIV video recordings;

Edit \ Image group \ BG removing \ Object bright - Used to generate a background image, and remove it from every image in the group in the case of bright object in dark background;

Edit \ Image group \ BG removing \ Object dark - Used to generate a background image, and remove it from every image in the group in the case of dark object in bright background;

Edit \ Image group \ BG removing \ Object dark - Used to generate a background image, and remove it from every image in the group in the case of dark object in bright background;

Edit \ Image group \ Crop to BMP - Used to crop the portion in a selected frame for every image in the group, and linear transformation is applied to transfer the images into 8-bit BMP format;

Edit \ Image group \ Orientation - Used to mirror or rotate every image in the group;

Edit \ Image group \ Calibration - Used to calibrate distorted images in a group;

Edit \ Image group \ Overlap + - Used to overlap all the images in a group by using the maximum gray values;

Edit \ Image group \ Overlap - - Used to overlap all the images in a group by using the minimum gray values;

Edit \ Average - Used to average all the images in a group;

Edit \ Orientation \ Rotation ’ - Used to rotate the current image with a given angle;

Edit \ Orientation \ Mirror X’ - Used to mirror the current image vertically;

Edit \ Orientation \ Mirror Y’ - Used to mirror the current image horizontally;

Edit \ Orientation \ Shift ‘- Used to activate functions for shifting the current image;

Edit \ Painting \ Fill in frame - Used to fill in a selected frame with selected pattern and gray value on the current image. Note that this function does not work for pixels whose gray value is 0 or 255. See dialogue box “Filling”; 

Edit \ Painting \ Line & fill - Used to draw lines with selected gray value on the current image and fill the area enclosed with several lines. When clicking this menu, a gray value is selected in a dialogue box, and the “TJ” button that can be used to cancel this function appears. A line can be drawn by first clicking the left mouse at one end of the line, and second clicking the left mouse at the other end. The filling is activated with a right mouse click in the selected area. The function is completed by press “TJ” button;

Edit \ Painting \ Paste - Used to past a round or square area of selected size with selected gray value on the current image;

Menu group “Edit – Special operations”

Edit \ Particle processing \ Particle identification - Used to identify the position, size, brightness, and shape of particles in the current image;

Edit \ Particle processing \ Position search #1 - Used to search for particle image positions with a complete identification of particle images, error less than one pixel;

Edit \ Particle processing \ Position search #2 - Used to search for particle image positions with a simple identification of particle images, error less than particle image diameter;

Edit \ Particle processing \ Particle contour - Used to determine particle image contours with a selected gray value threshold;

Edit \ Frame separation \ Double recording \ x-cut - Used to split a vertically arranged double recording (e.g. LAVISION or DANTEC IMG-file) in buffer recording 1 into two frames, when buffer recording 2 is free.

Edit \ Frame separation \ Double recording \ y-cut - Used to split a horizontally arranged double recording (e.g. IDT IMG-file) in buffer recording 1 into two frames, when buffer recording 2 is free.

Edit \ Frame separation \ Video recording - Used to split a video recording in buffer recording 1 into two frames, when buffer recording 2 is free.

Menu group “Edit – Distorted image”

Edit \ Stereo effect \ by parameters - Used to simulate the image distortion effect according to parameters of a stereo PIV system;

Edit \ Stereo effect \ by function - Used to simulate the image distortion effect according to calibration function of the stereo PIV system;

Edit \ Calibration - Used to calibrate the current distorted PIV image with selected calibration function to get an undistorted image. This function can be used to calibrate a portion of the distorted image in a selected frame;

Edit \ Test grid - Used to generate a regular grid image for test purposes.

Menu group “Tools – Particle image simulation”

Tools \ Simulation settings \ Particle  - Used to determine parameters of simulated particles;

Tools \ Simulation settings \ Stereo - Used to determine parameters of simulated stereo PIV system;

Tools \ Simulation settings \ Noise - Used to determine parameters of simulated imaging noise;

Tools \ Simulation settings \ Flow - Used to determine parameters for simulated flow;

Tools \ Simulation settings \ Clear - Used to reset simulation parameters;

Tools \ Successive frames - Used to generate synthetic PIV recordings of successive frames with a given number;

Tools \ BOS background  - Used to generate a background image for the Background Oriented Schlieren technique;

Tools \ Group of pairs - Used to generate a group of synthetic PIV recording pairs;

Tools \ IPT simulation - Used to generate successive image frames for particle image pattern tracking.

Tools \ Single frame - Used to generate a synthetic PIV image frame;

Tools \ One pair - Used to generate one synthetic PIV recording pair.

Menu group “View”

View \ Statistics - Used to display the minimum, maximum, mean and standard deviation of gray values in the current image;

View \ Frame - Used to draw a frame of given size by using a mouse click;

View \ data - Used to open “Data” window to check particle information.

Edpiv pE 2013 help