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Filters are point-wise operations, such as thresholding, or generally local operations producing a value based on the data in the vicinity of each point: gradients, step detectors and convolutions. Some simple common point-wise operations, e.g. value inversion, are also found in base GwyDataField methods.
void
gwy_data_field_normalize (GwyDataField *data_field
);
Normalizes data in a data field to range 0.0 to 1.0.
It is equivalent to gwy_data_field_renormalize(data_field
, 1.0, 0.0);
If data_field
is filled with only one value, it is changed to 0.0.
void gwy_data_field_renormalize (GwyDataField *data_field
,gdouble range
,gdouble offset
);
Transforms data in a data field with linear function to given range.
When range
is positive, the new data range is (offset
, offset
+range
); when range
is negative, the new data
range is (offset
-range
, offset
). In neither case the data are flipped, negative range only means different
selection of boundaries.
When range
is zero, this method is equivalent to gwy_data_field_fill(data_field
, offset
).
void gwy_data_field_area_renormalize (GwyDataField *data_field
,gint col
,gint row
,gint width
,gint height
,gdouble range
,gdouble offset
);
Transforms data in a part of a data field with linear function to given range.
When range
is positive, the new data range is (offset
, offset
+range
); when range
is negative, the new data
range is (offset
-range
, offset
). In neither case the data are flipped, negative range only means different
selection of boundaries.
When range
is zero, this method is equivalent to gwy_data_field_fill(data_field
, offset
).
data_field |
A data field. |
|
col |
Upper-left column coordinate. |
|
row |
Upper-left row coordinate. |
|
width |
Area width (number of columns). |
|
height |
Area height (number of rows). |
|
range |
New data interval size. |
|
offset |
New data interval offset. |
Since: 2.45
gint gwy_data_field_threshold (GwyDataField *data_field
,gdouble threshval
,gdouble bottom
,gdouble top
);
Tresholds values of a data field.
Values smaller than threshold
are set to value bottom
, values higher than threshold
or equal to it are set to
value top
gint gwy_data_field_area_threshold (GwyDataField *data_field
,gint col
,gint row
,gint width
,gint height
,gdouble threshval
,gdouble bottom
,gdouble top
);
Tresholds values of a rectangular part of a data field.
Values smaller than threshold
are set to value bottom
, values higher than threshold
or equal to it are set to
value top
gint gwy_data_field_clamp (GwyDataField *data_field
,gdouble bottom
,gdouble top
);
Limits data field values to a range.
gint gwy_data_field_area_clamp (GwyDataField *data_field
,gint col
,gint row
,gint width
,gint height
,gdouble bottom
,gdouble top
);
Limits values in a rectangular part of a data field to a range.
void gwy_data_field_area_gather (GwyDataField *data_field
,GwyDataField *result
,GwyDataField *buffer
,gint hsize
,gint vsize
,gboolean average
,gint col
,gint row
,gint width
,gint height
);
Sums or averages values in reactangular areas around each sample in a data field.
When the gathered area extends out of calculation area, only samples from their intersection are taken into the local sum (or average).
There are no restrictions on values of hsize
and vsize
with regard to width
and height
, but they have to be
positive.
The result is calculated by the means of two-dimensional rolling sums. One one hand it means the calculation time
depends linearly on (width
+ hsize
)*(height
+ vsize
) instead of width
*hsize
*height
*vsize
. On the other
hand it means absolute rounding errors of all output values are given by the largest input values, that is relative
precision of results small in absolute value may be poor.
data_field |
A data field. |
|
result |
A data field to put the result to, it may be |
|
buffer |
A data field to use as a scratch area, its size must be at least |
|
col |
Upper-left column coordinate. |
|
row |
Upper-left row coordinate. |
|
width |
Area width (number of columns). |
|
height |
Area height (number of rows). |
|
hsize |
Horizontal size of gathered area. The area is centered around each sample if |
|
vsize |
Vertical size of gathered area. The area is centered around each sample if |
|
average |
|
void gwy_data_field_convolve (GwyDataField *data_field
,GwyDataField *kernel_field
);
Convolves a data field with given kernel.
Note that the convolution is done by summation and can be slow for large kernels.
void gwy_data_field_area_convolve (GwyDataField *data_field
,GwyDataField *kernel_field
,gint col
,gint row
,gint width
,gint height
);
Convolves a rectangular part of a data field with given kernel.
Note that the convolution is done by summation and can be slow for large kernels.
data_field |
A data field to convolve. It must be at least as large as 1/3 of |
|
kernel_field |
Kenrel field to convolve |
|
col |
Upper-left column coordinate. |
|
row |
Upper-left row coordinate. |
|
width |
Area width (number of columns). |
|
height |
Area height (number of rows). |
void gwy_data_field_fft_convolve (GwyDataField *data_field
,GwyDataField *kernel_field
);
Convolves a data field with given kernel of the same size using FFT.
This is a simple FFT-based convolution done by multiplication in the frequency domain.
This is a somewhat low-level function. There is no padding or boundary treatment; images are considered periodic.
The result is normalised as if the convolution was done by summation and the physical units of data_field
are
unchanged.
Also note that in order to obtain unshifted result, the kernel needs to be centered around the top left corner.
You can use gwy_data_field_2dfft_dehumanize()
to transform a centered kernel.
data_field |
A data field to convolve. |
|
kernel_field |
Kenrel field to convolve |
Since: 2.54
void gwy_data_field_area_ext_convolve (GwyDataField *field
,guint col
,guint row
,guint width
,guint height
,GwyDataField *target
,GwyDataField *kernel
,GwyExteriorType exterior
,gdouble fill_value
,gboolean as_integral
);
Convolve a field with a two-dimensional kernel.
Pixel dimensions of target
may match either field
or just the rectangular area. In the former case the result is
written in the same rectangular area; in the latter case the result fills the entire target
.
The convolution is performed with the kernel centred on the respective field pixels. For directions in which the kernel has an odd size this holds precisely. For an even-sized kernel this means the kernel centre is placed 0.5 pixel left or up (towards lower indices) from the respective field pixel.
See gwy_data_field_extend()
for what constitutes the exterior and how it is handled.
If as_integral
is FALSE
the function performs a simple discrete convolution sum and the value units of target
are set to product of field
and kernel
units.
If as_integral
is TRUE
the function approximates a convolution integral. In this case kernel
should be a sampled
continuous transfer function. The units of value target
are set to product of field
and kernel
value units and
field
lateral units squared. Furthermore, the discrete sum is multiplied by the pixel size (i.e. dx
dy
in the
integral).
In either case, the lateral units and pixel size of kernel
are assumed to be the same as for field
(albeit not
checked), because the convolution does not make sense otherwise.
field |
A two-dimensional data field. |
|
col |
Upper-left column coordinate. |
|
row |
Upper-left row coordinate. |
|
width |
Area width (number of columns). |
|
height |
Area height (number of rows). |
|
target |
A two-dimensional data field where the result will be placed. It may be |
|
kernel |
Kernel to convolve |
|
exterior |
Exterior pixels handling. |
|
fill_value |
The value to use with |
|
as_integral |
|
Since: 2.49
void gwy_data_field_convolve_1d (GwyDataField *data_field
,GwyDataLine *kernel_line
,GwyOrientation orientation
);
Convolves a data field with given linear kernel.
data_field |
A data field to convolve. It must be at least as large as 1/3 of |
|
kernel_line |
Kenrel line to convolve |
|
orientation |
Filter orientation (see |
Since: 2.4
void gwy_data_field_area_convolve_1d (GwyDataField *data_field
,GwyDataLine *kernel_line
,GwyOrientation orientation
,gint col
,gint row
,gint width
,gint height
);
Convolves a rectangular part of a data field with given linear kernel.
For large separable kernels it can be more efficient to use a sequence of horizontal and vertical convolutions instead one 2D convolution.
data_field |
A data field to convolve. It must be at least as large as 1/3 of |
|
kernel_line |
Kernel line to convolve |
|
orientation |
Filter orientation ( |
|
col |
Upper-left column coordinate. |
|
row |
Upper-left row coordinate. |
|
width |
Area width (number of columns). |
|
height |
Area height (number of rows). |
Since: 2.4
void gwy_data_field_area_ext_row_convolve (GwyDataField *field
,guint col
,guint row
,guint width
,guint height
,GwyDataField *target
,GwyDataLine *kernel
,GwyExteriorType exterior
,gdouble fill_value
,gboolean as_integral
);
Convolve a field row-wise with a one-dimensional kernel.
Pixel dimensions of target
may match either field
or just the rectangular area. In the former case the result is
written in the same rectangular area; in the latter case the result fills the entire target
.
The convolution is performed with the kernel centred on the respective field pixels. For an odd-sized kernel this holds precisely. For an even-sized kernel this means the kernel centre is placed 0.5 pixel to the left (towards lower column indices) from the respective field pixel.
See gwy_data_field_extend()
for what constitutes the exterior and how it is handled.
If as_integral
is FALSE
the function performs a simple discrete convolution sum and the value units of target
are set to product of field
and kernel
units.
If as_integral
is TRUE
the function approximates a convolution integral. In this case kernel
should be a sampled
continuous transfer function. The units of value target
are set to product of field
and kernel
value units and
field
lateral units. Furthermore, the discrete sum is multiplied by the pixel size (i.e. dx
in the integral).
In either case, the lateral units and pixel size of kernel
are assumed to be the same as for a field
's row
(albeit not checked), because the convolution does not make sense otherwise.
field |
A two-dimensional data field. |
|
col |
Upper-left column coordinate. |
|
row |
Upper-left row coordinate. |
|
width |
Area width (number of columns). |
|
height |
Area height (number of rows). |
|
target |
A two-dimensional data field where the result will be placed. It may be |
|
kernel |
Kernel to convolve |
|
exterior |
Exterior pixels handling. |
|
fill_value |
The value to use with |
|
as_integral |
|
Since: 2.49
void gwy_data_field_filter_median (GwyDataField *data_field
,gint size
);
Filters a data field with median filter.
This method uses a simple square kernel. Use the general function
gwy_data_field_area_filter_kth_rank()
to perform filtering with different,
for instance circular, kernel.
void gwy_data_field_area_filter_median (GwyDataField *data_field
,gint size
,gint col
,gint row
,gint width
,gint height
);
Filters a rectangular part of a data field with median filter.
This method uses a simple square kernel. Use the general function
gwy_data_field_area_filter_kth_rank()
to perform filtering with different,
for instance circular, kernel.
void gwy_data_field_filter_mean (GwyDataField *data_field
,gint size
);
Filters a data field with mean filter of size size
.
This method is a simple gwy_data_field_area_gather()
wrapper, so the kernel is square. Use convolution
gwy_data_field_area_ext_convolve()
to perform a mean filter with different, for instance circular, kernel.
void gwy_data_field_area_filter_mean (GwyDataField *data_field
,gint size
,gint col
,gint row
,gint width
,gint height
);
Filters a rectangular part of a data field with mean filter of size size
.
This method is a simple gwy_data_field_area_gather()
wrapper, so the kernel is square. Use convolution
gwy_data_field_area_ext_convolve()
to perform a mean filter with different, for instance circular, kernel.
void gwy_data_field_filter_conservative (GwyDataField *data_field
,gint size
);
Filters a data field with conservative denoise filter.
void gwy_data_field_area_filter_conservative (GwyDataField *data_field
,gint size
,gint col
,gint row
,gint width
,gint height
);
Filters a rectangular part of a data field with conservative denoise filter.
void
gwy_data_field_filter_laplacian (GwyDataField *data_field
);
Filters a data field with Laplacian filter.
void gwy_data_field_area_filter_laplacian (GwyDataField *data_field
,gint col
,gint row
,gint width
,gint height
);
Filters a rectangular part of a data field with Laplacian filter.
void
gwy_data_field_filter_laplacian_of_gaussians
(GwyDataField *data_field
);
Filters a data field with Laplacian of Gaussians filter.
Since: 2.23
void gwy_data_field_area_filter_laplacian_of_gaussians (GwyDataField *data_field
,gint col
,gint row
,gint width
,gint height
);
Filters a rectangular part of a data field with Laplacian of Gaussians filter.
data_field |
A data field to apply the filter to. |
|
col |
Upper-left column coordinate. |
|
row |
Upper-left row coordinate. |
|
width |
Area width (number of columns). |
|
height |
Area height (number of rows). |
Since: 2.23
void gwy_data_field_filter_sobel (GwyDataField *data_field
,GwyOrientation orientation
);
Filters a data field with a directional Sobel filter.
void gwy_data_field_area_filter_sobel (GwyDataField *data_field
,GwyOrientation orientation
,gint col
,gint row
,gint width
,gint height
);
Filters a rectangular part of a data field with a directional Sobel filter.
void
gwy_data_field_filter_sobel_total (GwyDataField *data_field
);
Filters a data field with total Sobel filter.
Since: 2.31
void gwy_data_field_filter_prewitt (GwyDataField *data_field
,GwyOrientation orientation
);
Filters a data field with Prewitt filter.
void gwy_data_field_area_filter_prewitt (GwyDataField *data_field
,GwyOrientation orientation
,gint col
,gint row
,gint width
,gint height
);
Filters a rectangular part of a data field with a directional Prewitt filter.
void
gwy_data_field_filter_prewitt_total (GwyDataField *data_field
);
Filters a data field with total Prewitt filter.
Since: 2.31
void gwy_data_field_filter_slope (GwyDataField *data_field
,GwyDataField *xder
,GwyDataField *yder
);
Calculates x and y derivaties for an entire field.
The derivatives are calculated as the simple symmetrical differences (in physical units, not pixel-wise), except at the edges where the differences are one-sided.
Since: 2.37
void gwy_data_field_filter_gauss_step (GwyDataField *data_field
,gdouble sigma
);
Processes a data field with Gaussian step detection filter.
The filter is a multi-directional combination of convolutions with Gaussian multiplied by a signed step function.
The resulting values correspond roughly to the step height around the pixel.
Since: 2.54
void
gwy_data_field_filter_dechecker (GwyDataField *data_field
);
Filters a data field with 5x5 checker pattern removal filter.
Since: 2.1
void gwy_data_field_area_filter_dechecker (GwyDataField *data_field
,gint col
,gint row
,gint width
,gint height
);
Filters a rectangular part of a data field with 5x5 checker pattern removal filter.
data_field |
A data field to apply the filter to. |
|
col |
Upper-left column coordinate. |
|
row |
Upper-left row coordinate. |
|
width |
Area width (number of columns). |
|
height |
Area height (number of rows). |
Since: 2.1
void gwy_data_field_filter_gaussian (GwyDataField *data_field
,gdouble sigma
);
Filters a data field with a Gaussian filter.
data_field |
A data field to apply the filter to. |
|
sigma |
The sigma parameter of the Gaussian. |
Since: 2.4
void gwy_data_field_area_filter_gaussian (GwyDataField *data_field
,gdouble sigma
,gint col
,gint row
,gint width
,gint height
);
Filters a rectangular part of a data field with a Gaussian filter.
The Gausian is normalized, i.e. it is sum-preserving.
data_field |
A data field to apply the filter to. |
|
sigma |
The sigma parameter of the Gaussian. |
|
col |
Upper-left column coordinate. |
|
row |
Upper-left row coordinate. |
|
width |
Area width (number of columns). |
|
height |
Area height (number of rows). |
Since: 2.4
void gwy_data_field_row_gaussian (GwyDataField *data_field
,gdouble sigma
);
Filters a data field with a Gaussian filter in horizontal direction.
The Gausian is normalized, i.e. it is sum-preserving.
data_field |
A data field to apply the filter to. |
|
sigma |
The sigma parameter of the Gaussian. |
Since: 2.54
void gwy_data_field_column_gaussian (GwyDataField *data_field
,gdouble sigma
);
Filters a data field with a Gaussian filter in vertical direction.
The Gausian is normalized, i.e. it is sum-preserving.
data_field |
A data field to apply the filter to. |
|
sigma |
The sigma parameter of the Gaussian. |
Since: 2.54
void gwy_data_field_filter_minimum (GwyDataField *data_field
,gint size
);
Filters a data field with minimum filter.
This method uses a simple square kernel. Use the general function
gwy_data_field_area_filter_min_max()
to perform filtering with different,
for instance circular, kernel.
void gwy_data_field_area_filter_minimum (GwyDataField *data_field
,gint size
,gint col
,gint row
,gint width
,gint height
);
Filters a rectangular part of a data field with minimum filter.
This operation is often called erosion filter.
This method uses a simple square kernel. Use the general function
gwy_data_field_area_filter_min_max()
to perform filtering with different,
for instance circular, kernel.
void gwy_data_field_filter_maximum (GwyDataField *data_field
,gint size
);
Filters a data field with maximum filter.
This method uses a simple square kernel. Use the general function
gwy_data_field_area_filter_min_max()
to perform filtering with different,
for instance circular, kernel.
void gwy_data_field_area_filter_maximum (GwyDataField *data_field
,gint size
,gint col
,gint row
,gint width
,gint height
);
Filters a rectangular part of a data field with maximum filter.
This operation is often called dilation filter.
This method uses a simple square kernel. Use the general function
gwy_data_field_area_filter_min_max()
to perform filtering with different,
for instance circular, kernel.
void gwy_data_field_area_filter_min_max (GwyDataField *data_field
,GwyDataField *kernel
,GwyMinMaxFilterType filtertype
,gint col
,gint row
,gint width
,gint height
);
Applies a morphological operation with a flat structuring element to a part of a data field.
Morphological operations with flat structuring elements can be expressed using minimum (erosion) and maximum (dilation) filters that are the basic operations this function can perform.
The kernel field is a mask that defines the shape of the flat structuring
element. It is reflected for all maximum operations (dilation). For
symmetrical kernels this does not matter. You can use
gwy_data_field_elliptic_area_fill()
to create a true circular (or
elliptical) kernel.
The kernel is implicitly centered, i.e. it will be applied symmetrically to avoid unexpected data movement. Even-sized kernels (generally not recommended) will extend farther towards the top left image corner for minimum (erosion) and towards the bottom right corner for maximum (dilation) operations due to the reflection. If you need off-center structuring elements you can add empty rows or columns to one side of the kernel to counteract the symmetrisation.
The operation is linear-time in kernel size for any convex kernel. Note
gwy_data_field_area_filter_minimum()
and
gwy_data_field_area_filter_maximum()
, which are limited to square
structuring elements, are much faster for large sizes of the squares.
The exterior is always handled as GWY_EXTERIOR_BORDER_EXTEND
.
data_field |
A data field to apply the filter to. |
|
kernel |
Data field defining the flat structuring element. |
|
filtertype |
The type of filter to apply. |
|
col |
Upper-left column coordinate. |
|
row |
Upper-left row coordinate. |
|
width |
Area width (number of columns). |
|
height |
Area height (number of rows). |
Since: 2.43
void gwy_data_field_area_filter_disc_asf (GwyDataField *data_field
,gint radius
,gboolean closing
,gint col
,gint row
,gint width
,gint height
);
Applies an alternating sequential morphological filter with a flat disc structuring element to a part of a data field.
Alternating sequential filter is a filter consisting of repeated opening and
closing (or closing and opening) with progressively larger structuring
elements. This function performs such filtering for sequence of structuring
elements consisting of true Euclidean discs with increasing radii. The
largest disc in the sequence fits into a (2size
+ 1) × (2size
+ 1) square.
data_field |
A data field to apply the filter to. |
|
radius |
Maximum radius of the circular structuring element, in pixels. For radius 0 and smaller the filter is no-op. |
|
closing |
|
|
col |
Upper-left column coordinate. |
|
row |
Upper-left row coordinate. |
|
width |
Area width (number of columns). |
|
height |
Area height (number of rows). |
Since: 2.43
gboolean gwy_data_field_area_filter_kth_rank (GwyDataField *data_field
,GwyDataField *kernel
,gint col
,gint row
,gint width
,gint height
,gint k
,GwySetFractionFunc set_fraction
);
Applies a k
-th rank filter to a part of a data field.
Pass half the number of non-zero values in kernel
as k
for a median
filter.
The kernel field is a mask that defines the shape of the kernel. You can
use gwy_data_field_elliptic_area_fill()
to create a true circular (or
elliptical) kernel. The kernel must be non-empty.
The kernel is implicitly centered, i.e. it will be applied symmetrically to avoid unexpected data movement. Even-sized kernels (generally not recommended) will extend farther towards the top left image corner for minimum (erosion) and towards the bottom right corner for maximum (dilation) operations due to the reflection. If you need off-center structuring elements you can add empty rows or columns to one side of the kernel to counteract the symmetrisation.
The exterior is always handled as GWY_EXTERIOR_BORDER_EXTEND
.
If the operation is aborted the contents of data_field
is untouched.
data_field |
A data field to apply the filter to. |
|
kernel |
Data field defining the kernel shape. |
|
col |
Upper-left column coordinate. |
|
row |
Upper-left row coordinate. |
|
width |
Area width (number of columns). |
|
height |
Area height (number of rows). |
|
k |
Rank of the value to store as the output (from lowest to highest). |
|
set_fraction |
Function that sets fraction to output (or |
TRUE
if the operation was not aborted via set_fraction
returning FALSE
; FALSE
if it was aborted.
Since: 2.51
gboolean gwy_data_field_area_filter_trimmed_mean (GwyDataField *data_field
,GwyDataField *kernel
,gint col
,gint row
,gint width
,gint height
,gint nlowest
,gint nhighest
,GwySetFractionFunc set_fraction
);
Applies a trimmed mean filter to a part of a data field.
At least one value must remain after the trimming, i.e. nlowest
+ nhighest
must be smaller than the number of non-zero values in kernel
. Usually one
passes the same number as both nlowest
and nhighest
, but it is not
a requirement.
The kernel field is a mask that defines the shape of the kernel. You can
use gwy_data_field_elliptic_area_fill()
to create a true circular (or
elliptical) kernel. The kernel must be non-empty.
The kernel is implicitly centered, i.e. it will be applied symmetrically to avoid unexpected data movement. Even-sized kernels (generally not recommended) will extend farther towards the top left image corner for minimum (erosion) and towards the bottom right corner for maximum (dilation) operations due to the reflection. If you need off-center structuring elements you can add empty rows or columns to one side of the kernel to counteract the symmetrisation.
The exterior is always handled as GWY_EXTERIOR_BORDER_EXTEND
.
If the operation is aborted the contents of data_field
is untouched.
data_field |
A data field to apply the filter to. |
|
kernel |
Data field defining the kernel shape. |
|
col |
Upper-left column coordinate. |
|
row |
Upper-left row coordinate. |
|
width |
Area width (number of columns). |
|
height |
Area height (number of rows). |
|
nlowest |
The number of lowest values to discard. |
|
nhighest |
The number of highest values to discard. |
|
set_fraction |
Function that sets fraction to output (or |
TRUE
if the operation was not aborted via set_fraction
returning FALSE
; FALSE
if it was aborted.
Since: 2.53
void gwy_data_field_filter_rms (GwyDataField *data_field
,gint size
);
Filters a data field with RMS filter.
void gwy_data_field_area_filter_rms (GwyDataField *data_field
,gint size
,gint col
,gint row
,gint width
,gint height
);
Filters a rectangular part of a data field with RMS filter of size size
.
RMS filter computes root mean square in given area.
void
gwy_data_field_filter_kuwahara (GwyDataField *data_field
);
Filters a data field with Kuwahara filter.
void gwy_data_field_area_filter_kuwahara (GwyDataField *data_field
,gint col
,gint row
,gint width
,gint height
);
Filters a rectangular part of a data field with a Kuwahara (edge-preserving smoothing) filter.
void gwy_data_field_filter_canny (GwyDataField *data_field
,gdouble threshold
);
Filters a rectangular part of a data field with canny edge detector filter.
void gwy_data_field_shade (GwyDataField *data_field
,GwyDataField *target_field
,gdouble theta
,gdouble phi
);
Shades a data field.
void gwy_data_field_filter_harris (GwyDataField *x_gradient
,GwyDataField *y_gradient
,GwyDataField *result
,gint neighbourhood
,gdouble alpha
);
Applies Harris corner detection filter to a pair of gradient data fields.
All passed data field must have the same size.
void gwy_data_field_deconvolve_regularized (GwyDataField *dfield
,GwyDataField *operand
,GwyDataField *out
,gdouble sigma
);
Performs deconvolution of a data field using a simple regularization.
The operation can be used to deblur an image or conversely recover the point spread function from ideal response image.
Convolving the result with the operand using gwy_data_field_area_ext_convolve()
with as_integral
=TRUE
will
recover (approximately) the image. This means the deconvolution assumes continous convolution, not discrete sums.
Note that for the latter case this means the point spread function will be centered in out
.
For recovery of transfer function, dfield
and operand
should be windowed beforehand if they are not periodic.
dfield |
A data field. |
|
operand |
One of the factors entering the convolution resulting in |
|
out |
Data field where to put the result into. It will be resized to match |
|
sigma |
Regularization parameter. |
Since: 2.51
void gwy_data_field_deconvolve_psf_leastsq (GwyDataField *dfield
,GwyDataField *operand
,GwyDataField *out
,gdouble sigma
,gint border
);
Performs reconstruction of transfer function from convolved and ideal sharp images.
The transfer function is reconstructed by solving the corresponding least squares problem. This method is suitable
when the dimensions of out
are much smaller than the images.
Since the method accumulates errors close to edges, they can be removed within the procedure by reconstructing
a slightly larger transfer function and then cutting the result. The extension is given by border
, typical
suitable values are 2 or 3.
Convolving the result with the operand using gwy_data_field_area_ext_convolve()
with as_integral
=TRUE
will
recover (approximately) the image. This means the deconvolution assumes continous convolution, not discrete sums.
Note that for the latter case this means the point spread function will be centered in out
.
Fields dfield
and operand
should be windowed beforehand if they are not periodic.
dfield |
A data field. |
|
operand |
Ideal sharp measurement (before convolution). It must have the same dimensions as |
|
out |
Output field for the transfer function. Its dimensions are preserved and determine the transfer function
support. It must be smaller than half of |
|
sigma |
Regularization parameter. |
|
border |
Number of pixel to extend and cut off the transfer function. |
Since: 2.52
gdouble gwy_data_field_find_regularization_sigma_for_psf (GwyDataField *dfield
,GwyDataField *ideal
);
Finds regularization parameter for point spread function calculation using regularized deconvolution.
The estimated value should be suitable for reconstruction of the point spread function using
gwy_data_field_deconvolve_regularized()
. The estimate is only suitable for PSF, it does not work for image
sharpening using a known PSF.
Since: 2.51
gdouble gwy_data_field_find_regularization_sigma_leastsq (GwyDataField *dfield
,GwyDataField *ideal
,gint width
,gint height
,gint border
);
Finds regularization parameter for point spread function calculation using least squares method.
The estimated value should be suitable for reconstruction of the point spread function using
gwy_data_field_deconvolve_psf_leastsq()
.
dfield |
A data field with convolved noisy data. |
|
ideal |
A data field with ideal sharp data. |
|
width |
Horizontal size of transfer function support. |
|
height |
Vertical size of transfer function support. |
|
border |
Number of pixel to extend and cut off the transfer function. |
Since: 2.52