Image Processor¶
The Image Processor device can provide for each incoming image (2D) or spectrum (1D):
- the minimum, maximum and mean pixel value;
- the frequency distribution of pixel values;
- the image integrals in x and y directions (only for 2D images);
- the centre-of-mass and standard deviation;
- gaussian fit parameters for the x and y integrals (the latter only for 2D (images);
- gaussian fit parameters for the 2D image;
- pixel values integral over a region.
Each feature can be enabled or disabled by using the boolean properties listed in the General Settings section.
General settings of the Image Processor are described in the Enabling Features section.
Input to the Device¶
General Settings¶
The following properties affect all the algorithms ran in the device.
| Property key | Description |
|---|---|
| imagePath | The key where the image will be looked for in the
input data. The default value -
data.image - isusually appropriate when the input channel is
connected to imagers.
|
| filterImagesByThreshold | If
filterImagesByThreshold is True, onlyimages with maximum pixel value exceeding
imageThreshold will be processed. Others will bediscarded.
|
| imageThreshold | The threshold for processing an image. See above.
|
| absolutePositions | If
True, the centre-of-mass and fit results willtake into account the current settings for ROI and
binning.
|
| subtractBkgImage | Subtract the loaded background image.
|
| subtractImagePedestal | Subtract the image pedestal (i.e.
image = image -
image.min()).This is done after background subtraction.
|
Enabling Features¶
The different algorithms available can be enabled by setting the following boolean parameters.
| Property key | Description |
|---|---|
| doMinMaxMean | Get the following information from the pixels: min,
max, mean value.
|
| doBinCount | Calculate the frequency distribution of pixel values.
The distribution will be available in
data.imgBinCount. |
| doXYSum | Integrate the image along the x- and y-axes.
The distributions will be available in
data.imgXand
data.imgY. |
| doCOfM | Calculate centre-of-mass and widths.
|
| do1DFit | Perform a 1D gaussian fit of the x- and
y-distributions.
|
| do2DFit | Perform a 2D gaussian fits.
Be careful: It can be slow!
|
| doIntegration | Integrate the pixel values in the specified region.
|
Options for Centre-of-Mass¶
The user can define a range for the centre-of-mass calculation, and a pixel threshold to discard background pixels. More details are given in the table:
| Property key | Description |
|---|---|
| comRange | The range to be used for the centre-of-mass
calculation. Can be the full range, or a
user-defined one.
|
| userDefinedRange | The user-defined range for centre-of-mass,
gaussian fit(s) and integrales along the x & y axes.
|
| absThreshold | Pixels below this threshold will not be used for the
centre-of-mass calculation.
If greater than 0, the relative threshold will not be
used.
|
| threshold | Pixels below this relative threshold (fraction of the
highest value) will not be used for the
centre-of-mass calculation. It will only be applied
if no absolute threshold is set.
|
Options for Gaussian Fit¶
The Gaussian fit is done by using the fitGauss and fitGauss2DRot
functions available in the image processing package.
Initial parameters fit are calculated by the peakParametersEval function
in the imageProcessing package, when the “raw peak” option is choosen.
The user can define the range used for the Gaussian fit, enable a 1st order polynomial, define which initial fit parameters shall be used, enable rotation angle for the 2D Gaussian fit.
More details are given in the table:
| Property key | Description |
|---|---|
| pixelSize | The pixel size. It will be used when evaluating the
beam size.
|
| fitRange | The range to be used for fitting. Can be the full
range, an auto-determined, or the user-defined one.
|
| rangeForAuto | The automatic range for ‘auto’ mode (in standard
deviations).
|
| userDefinedRange | The user-defined range.
|
| enablePolynomial | Add a 1st order polynomial term (ramp) to gaussian
fits.
|
| gauss1dStartValues | Selects how 1d gaussian fit starting values are
evaluated. The options are: last fit result,
raw peak.
|
| doGaussRotation | Allow the 2D gaussian to be rotated.
|
Options for Integration¶
The user can define the region to be integrated over.
| Property key | Description |
|---|---|
| integrationRegion | The region to be integrated over.
|
Commands¶
The user can select the current image as background image.
| Slot key | Description |
|---|---|
| useAsBackgroundImage | Use the current image as background image.
|
Output of the Device¶
General properties¶
| Property key | Description |
|---|---|
| frameRate | The rate of incoming images. It is refreshed once per
second.
|
| imageWidth | The width of the incoming image.
|
| imageOffsetX | If the incoming image has a ROI, this represents the
X position of the top-left corner.
|
| imageBinningX | The image binning in the X direction.
|
| imageHeight | The height of the incoming image.
|
| imageOffsetY | If the incoming image has a ROI, this represents the
Y position of the top-left corner.
|
| imageBinningY | The image binning in the Y direction.
|
| minPxValue | The minimum image pixel value.
|
| maxPxValue | The maximum image pixel value.
|
| meanPxValue | The mean image pixel value.
|
Execution Time¶
The time spent in each part of the image processing is calculated and displayed in the device. The values are refreshed once per second.
| Property key | Description |
|---|---|
| minMaxMeanTime | Time spent for evaluating min, max, mean pixel value.
|
| binCountTime | Time spent for calculating the frequency distribution
of pixel values.
|
| subtractBkgImageTime | Time spent in subtracting the background image.
|
| subtractPedestalTime | Time spent in subtracting the image pedestal.
|
| xYSumTime | Time spent in integrating the image in X and Y.
|
| cOfMTime | Time spent in evaluating the centre-of-mass.
|
| xFitTime | Time spent in 1D Gaussian fit of the X distribution.
|
| yFitTime | Time spent in 1D Gaussian fit of the Y distribution.
|
| fitTime | Time spent in 2D Gaussian fit of the image.
|
| integrationTime | Time spent in integrating over a region.
|
Centre-of-Mass¶
| Property key | Description |
|---|---|
| x0 | X position of the centre-of-mass.
|
| sx | Standard deviation in X of the centre-of-mass.
|
| y0 | Y position of the centre-of-mass.
|
| sy | Standard deviation in Y of the centre-of-mass.
|
Gaussian Fit¶
By enabling the 1D fits, the image will be first integrated along Y- and X- directions, in order to give a 1D distribution. These distributions will be then fitted with a Gaussian.
| Property key | Description |
|---|---|
| xFitSuccess | 1D Gaussian fit success for the X distribution
(1-4 if fit converged).
|
| ax1d | Amplitude
Ax from 1D fit. |
| x01d | x0 peak position from 1D fit. |
| ex01d | Uncertainty on
x0 estimation. |
| sx1d | Standard deviation on
x0 from 1D fit. |
| esx1d | Uncertainty on standard deviation estimation.
|
| beamWidth1d | Beam width from 1D Fit. Defined as 4x
sx1d. |
| yFitSuccess | 1D Gaussian fit success for the Y distribution
(1-4 if fit converged).
|
| ay1d | Amplitude
Ay from 1D fit. |
| y01d | y0 peak position from 1D fit. |
| ey01d | Uncertainty on
y0 estimation. |
| sy1d | Standard deviation on
y0 from 1D fit. |
| esy1d | Uncertainty on standard deviation estimation.
|
| beamHeight1d | Beam height from 1D Fit. Defined as 4x
sy1d. |
By enabling the 2D fit, the 2D pixel distribution will be fitted. Be careful, for large images it could be quite slow, in particular if you enable rotation angle!
| Property key | Description |
|---|---|
| fitSuccess | 2D Gaussian fit success (1-4 if fit converged).
|
| a2d | Amplitude from 2D fit.
|
| x02d | x0 peak position from 2D fit. |
| ex02d | Uncertainty on
x0 estimation. |
| sx2d | Standard deviation on
x0 from 2D fit. |
| esx2d | Uncertainty on standard deviation estimation.
|
| beamWidth2d | Beam width from 2D Fit. Defined as 4x
sx2d. |
| y02d | y0 peak position from 2D fit. |
| ey02d | Uncertainty on
y0 estimation. |
| sy2d | Standard deviation on
y0 from 2D fit. |
| esy2d | Uncertainty on standard deviation estimation.
|
| beamHeight2d | Beam height from 2D Fit. Defined as 4x
sy2d. |
| theta2d | Rotation angle from 2D fit.
|
| etheta2d | Uncertainty on rotation angle estimation.
|
Integration¶
| Property key | Description |
|---|---|
| regionIntegral | Integral of pixel value over the specified region.
|
| regionMean | Mean pixel value over the specified region.
|
Other Outputs¶
The following vector properties are available in the output channel named output.
| Property key | Description |
|---|---|
| data.imgBinCount | Distribution of the image pixel counts.
|
| data.imgX | Image integral along the Y-axis.
|
| data.imgY | Image integral along the X-axis.
|
An example of pixel count distribution.