This class will enable you to mix multiple frames together.

 

The mixer class is enabled through the 2D Mode: "DB Class management" interface.  Once you have an instance of this class in your database tree, a new "Mixer" button will be present in the Modes menu.  This button will open the mixer's interface.

 

The "Discriminate Channels On" and "Associate Frames On" parameter are used to select which frames is mixed with which.  The user specify an equation that is used to compute the pixels of the mixed frames.  Each mixed frame can be composed from the pixels of multiple source frames.  Each of the frame that can be used to compose the mix is a "channel".  Usually the channels are series from the original acquisition.  If these channels have multiple frames each, then the "Associate Frames On" parameter is used to specify which of the frames within each channel are to be associated together.

 

Special key word can be used for these parameters. "Path", "Name" and "Suffix".  Using "Path" or "Suffix" in the "Discriminate Channels On" parameter can be used to compare the TAG results of the same GLI image segmented multiple times.  For repeatability studies, the same GLI image can be copied in different directories, segmented by different users and read back in sliceO.  The "Path" parameter can then be used to discriminate each instance of the GLI and an equation like "((T1-T2)>0) ? (T1-T2) : (T2-T1)" can be used to display the difference between each TAG results.

 

For example, the default values, Discriminate Channels On = "Series Description" (DICOM tag (0008,103E) and Associate Frames On = "Slice Location" (DICOM tag (0020,1041)) is used to mix frames from the MR IDEAL sequences.

 

The mixer's equation syntax

The mixer equation is used to specify the value of the pixels "mixed" image. The new pixel values are compute for each pixel of the mixed frames.  Depending on the type of the resulting image, you either have one equation (intensity for GLI images) or 3 equations (RGB color components for RGB images) for the pixel values of the image and 1 equation for the TAG values associated with the images.  These equations are evaluated for each pixels of the mixed frames each time you click on the "Update DB" button.

 

The mixer use the following terms:

N is the number of channels available.

Px represent the GLI pixel values of channel x

Tx represent the TAG pixel values of channel x

Rx, Gx, Bx represent the red, green and blue component of the pixels of channel x

MAXx, MINx, represent the maximum and minimum GLI pixel values of channel x

Vx represent the value of slider x

Si, Sj or Sk are used for summations of the following term over the N channels. (Ex: "SiPi / N" is the mean value of the pixels.)

 

In the previous terms, "x" can be the channel number (1 to N), the character "c" for the channel associated with the TAG value, or one of "i", "j" and "k" if you use a summation.

 

You can also use constants and sliceO variables in your equation.  Ex: $A + P1 * 255

 

These terms are combined together using the following operators:

 

And the functions:

 

 

The mathematical operators

+, -, *, / are the standard plus, minus, multiplication and division operators.

% is the modulo operator, A % B is replaced by the rest in the integer division of A by B.  Ex: 5 % 3 = 2

 

The test operators

A = B replaced by 1 if A equal to B, 0 otherwise

A < B replaced by 1 if A is smaller than B, 0 otherwise

A > B replaced by 1 if A is greater than B, 0 otherwise

 

The logical operators

| is a logical Or

& is a logical And

^ is a logical Xor

 

The conditional operator

The syntax is: Test ? A : B

if Test is true then A is evaluated

if Test is false then B is evaluated

 

The unari functions:

Use a syntax like: "abs(P1)" with 1 argument in parenthesis.

 

The binari functions:

Use a syntax like: "max(P1,P2)" with 2 comma separated arguments inside the parenthesis.

 

The sliceOmatic variables (starting with $) can also be used in the equations.

 

Ex: simple "cross fade" between 2 channels. Mixed pixels = channel 1 if V1=0, channel 2 if V1 = 1

(P1 * (1-V1)) + (P2 * V1)

 

Ex: Conditional statement with sliceO variable ($A).  The resulting pixels are normalized between 0 and 255

( P1 > $A ) ? (P1 / MAX1) * 255 : (P2 / MAX2) * 255

 

Ex: You can use parenthesis in summations.

Si(Pi-100) is equivalent to (P₁-100) + (P₂-100) + ... + (P_N-100)

 

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From the Graphic Interface

 

 

 

 

 

 

 

 

 

 

From the Display Area

 

There is no display area interaction specific to this class.

 

 

From the Keyboard

 

The following commands can also be mapped to keyboard keys as a shortcut:

 

 

 

From the Command Line

 

System Variables defined in this library:

 

 

Commands recognized in this library:

 

Mixer: Mode (GLI|RGB)

Set the current mixer mode.  The values are: 0 for GLI and 128 for RGB.

 

Mixer: Equation (GLI|TAG|Red|Grn|Blu) Equation

Set the one of the equations to the string "equation" (be sure to protect it with quotes).

 

Mixer: Tag [t_level] channel_id

Set the "Tag" parameter for the different levels of the class. This parameter is used to select which of the channels will have the associated TAG files.  The TAG files are accessible by all channels, but when they are saved, the file name is based on the selected channel.

 

Mixer: Associate [t_level] group element

Set the "Associate" parameter for the different levels of the class.

 

Mixer: Discriminate [t_level] group element

Set the "Discriminate" parameter for the different levels of the class.

 

Mixer: Bypass [t_level] [channel] (on|off|toggle)

Set the "Bypass" parameter for the different levels of the channels.

 

Templates: