gray_projectionsGrayProjectionsGrayProjectionsgray_projectionsT_gray_projections🔗

Short description🔗

gray_projectionsGrayProjectionsGrayProjectionsgray_projectionsT_gray_projections — Calculate horizontal and vertical gray-value projections.

Signature🔗

gray_projections( region Region, image Image, string Mode, out real HorProjection, out real VertProjection )

Description🔗

gray_projectionsGrayProjections calculates the horizontal and vertical gray-value projections, i.e., the mean values in the horizontal and vertical direction of the gray values of the input image Imageimageimage within the input region Regionregionregion.

If Modemodemode = 'simple'"simple" is selected the projection is performed in the direction of the coordinate axes of the image, i.e.:

\[\begin{eqnarray*} \textrm{HorProjection}(r) & = & \frac{1}{n(r+r')} \sum_{(r+r',c+c') \in \textrm{Region}} \textrm{Image}(r+r',c+c') \\ \textrm{VertProjection}(c) & = & \frac{1}{n(c+c')} \sum_{(r+r',c+c') \in \textrm{Region}} \textrm{Image}(r+r',c+c') \end{eqnarray*}\]

Here, \((r',c')\) denotes the upper left corner of the smallest enclosing axis-parallel rectangle of the input region (see smallest_rectangle1SmallestRectangle1), and \(n(x)\) denotes the number of region points in the corresponding row \(r+r'\) or column \(c+c'\). Hence, the horizontal projection returns a one-dimensional function that reflects the vertical gray value changes. Likewise, the vertical projection returns a function that reflects the horizontal gray value changes.

If Modemodemode = 'rectangle'"rectangle"is selected the projection is performed in the direction of the major axes of the smallest enclosing rectangle of arbitrary orientation of the input region (see smallest_rectangle2SmallestRectangle2). Here, the horizontal projection direction corresponds to the larger axis, while the vertical direction corresponds to the smaller axis. In this mode, all gray values within the smallest enclosing rectangle of arbitrary orientation of the input region are used to compute the projections.

Attention🔗

The operator gray_projectionsGrayProjections only considers the given Regionregionregion and ignores any previously set domain of the input image Imageimageimage.

If \(n(x) = 0\), i.e., if there are no region points in the corresponding row \(r+r'\) or column \(c+c'\), the respective value of HorProjectionhorProjectionhor_projection or VertProjectionvertProjectionvert_projection is set to \(-1\).

gray_projectionsGrayProjections can be executed on an OpenCL device for the 'simple'"simple" mode if the OpenCL device supports the cl_khr_global_int32_base_atomics OpenCL extension. For processing images of type real, the OpenCL device must support the cl_khr_fp64 and cl_khr_int64_base_atomics extensions.

Execution information🔗

Execution information

Supports OpenCL compute devices.
Multithreading type: reentrant (runs in parallel with non-exclusive operators).
Multithreading scope: global (may be called from any thread).
Processed without parallelization.

Parameters🔗

Regionregionregion (input_object) region → objectHObjectHRegionHObjectHobject

Region to be processed.

Imageimageimage (input_object) singlechannelimage → object (byte* / int2* / uint2* / real*)HImage (byte* / int2* / uint2* / real*) *allowed for compute devices

Grayvalues for projections.

Modemodemode (input_control) string → (string)HTuple (HString)HTuple (string)strHtuple (char*)

Method to compute the projections.

Default: 'simple'"simple"
List of values: 'rectangle', 'simple'"rectangle", "simple"
List of values (for compute devices): 'simple'"simple"

HorProjectionhorProjectionhor_projection (output_control) real-array → (real)HTuple (double)HTuple (double)Sequence[float]Htuple (double)

Horizontal projection.

VertProjectionvertProjectionvert_projection (output_control) real-array → (real)HTuple (double)HTuple (double)Sequence[float]Htuple (double)

Vertical projection.

Module🔗

1D Metrology