filters

filters — Convolution and other 2D data filters

Synopsis

#include <libprocess/gwyprocess.h>

void                gwy_data_field_normalize            (GwyDataField *data_field);
void                gwy_data_field_renormalize          (GwyDataField *data_field,
                                                         gdouble range,
                                                         gdouble offset);
gint                gwy_data_field_threshold            (GwyDataField *data_field,
                                                         gdouble threshval,
                                                         gdouble bottom,
                                                         gdouble top);
gint                gwy_data_field_area_threshold       (GwyDataField *data_field,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height,
                                                         gdouble threshval,
                                                         gdouble bottom,
                                                         gdouble top);
gint                gwy_data_field_clamp                (GwyDataField *data_field,
                                                         gdouble bottom,
                                                         gdouble top);
gint                gwy_data_field_area_clamp           (GwyDataField *data_field,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height,
                                                         gdouble bottom,
                                                         gdouble top);
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);
void                gwy_data_field_convolve             (GwyDataField *data_field,
                                                         GwyDataField *kernel_field);
void                gwy_data_field_area_convolve        (GwyDataField *data_field,
                                                         GwyDataField *kernel_field,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_convolve_1d          (GwyDataField *data_field,
                                                         GwyDataLine *kernel_line,
                                                         GwyOrientation orientation);
void                gwy_data_field_area_convolve_1d     (GwyDataField *data_field,
                                                         GwyDataLine *kernel_line,
                                                         GwyOrientation orientation,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_median        (GwyDataField *data_field,
                                                         gint size);
void                gwy_data_field_area_filter_median   (GwyDataField *data_field,
                                                         gint size,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_mean          (GwyDataField *data_field,
                                                         gint size);
void                gwy_data_field_area_filter_mean     (GwyDataField *data_field,
                                                         gint size,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_conservative  (GwyDataField *data_field,
                                                         gint size);
void                gwy_data_field_area_filter_conservative
                                                        (GwyDataField *data_field,
                                                         gint size,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_laplacian     (GwyDataField *data_field);
void                gwy_data_field_area_filter_laplacian
                                                        (GwyDataField *data_field,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_laplacian_of_gaussians
                                                        (GwyDataField *data_field);
void                gwy_data_field_area_filter_laplacian_of_gaussians
                                                        (GwyDataField *data_field,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_sobel         (GwyDataField *data_field,
                                                         GwyOrientation orientation);
void                gwy_data_field_area_filter_sobel    (GwyDataField *data_field,
                                                         GwyOrientation orientation,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_sobel_total   (GwyDataField *data_field);
void                gwy_data_field_filter_prewitt       (GwyDataField *data_field,
                                                         GwyOrientation orientation);
void                gwy_data_field_area_filter_prewitt  (GwyDataField *data_field,
                                                         GwyOrientation orientation,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_prewitt_total (GwyDataField *data_field);
void                gwy_data_field_filter_dechecker     (GwyDataField *data_field);
void                gwy_data_field_area_filter_dechecker
                                                        (GwyDataField *data_field,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_gaussian      (GwyDataField *data_field,
                                                         gdouble sigma);
void                gwy_data_field_area_filter_gaussian (GwyDataField *data_field,
                                                         gdouble sigma,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_minimum       (GwyDataField *data_field,
                                                         gint size);
void                gwy_data_field_area_filter_minimum  (GwyDataField *data_field,
                                                         gint size,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_maximum       (GwyDataField *data_field,
                                                         gint size);
void                gwy_data_field_area_filter_maximum  (GwyDataField *data_field,
                                                         gint size,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_rms           (GwyDataField *data_field,
                                                         gint size);
void                gwy_data_field_area_filter_rms      (GwyDataField *data_field,
                                                         gint size,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_kuwahara      (GwyDataField *data_field);
void                gwy_data_field_area_filter_kuwahara (GwyDataField *data_field,
                                                         gint col,
                                                         gint row,
                                                         gint width,
                                                         gint height);
void                gwy_data_field_filter_canny         (GwyDataField *data_field,
                                                         gdouble threshold);
void                gwy_data_field_shade                (GwyDataField *data_field,
                                                         GwyDataField *target_field,
                                                         gdouble theta,
                                                         gdouble phi);
void                gwy_data_field_filter_harris        (GwyDataField *x_gradient,
                                                         GwyDataField *y_gradient,
                                                         GwyDataField *result,
                                                         gint neighbourhood,
                                                         gdouble alpha);

Description

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.

Details

gwy_data_field_normalize ()

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.

data_field :

A data field.

gwy_data_field_renormalize ()

void                gwy_data_field_renormalize          (GwyDataField *data_field,
                                                         gdouble range,
                                                         gdouble offset);

Transforms data in a data field with first 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.

range :

New data interval size.

offset :

New data interval offset.

gwy_data_field_threshold ()

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

data_field :

A data field.

threshval :

Threshold value.

bottom :

Lower replacement value.

top :

Upper replacement value.

Returns :

The total number of values above threshold.

gwy_data_field_area_threshold ()

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

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).

threshval :

Threshold value.

bottom :

Lower replacement value.

top :

Upper replacement value.

Returns :

The total number of values above threshold.

gwy_data_field_clamp ()

gint                gwy_data_field_clamp                (GwyDataField *data_field,
                                                         gdouble bottom,
                                                         gdouble top);

Limits data field values to a range.

data_field :

A data field.

bottom :

Lower limit value.

top :

Upper limit value.

Returns :

The number of changed values, i.e., values that were outside [bottom, top].

gwy_data_field_area_clamp ()

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.

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).

bottom :

Lower limit value.

top :

Upper limit value.

Returns :

The number of changed values, i.e., values that were outside [bottom, top].

gwy_data_field_area_gather ()

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 data_field itself.

buffer :

A data field to use as a scratch area, its size must be at least width*height. May be NULL to allocate a private temporary buffer.

hsize :

Horizontal size of gathered area. The area is centered around each sample if hsize is odd, it extends one pixel more to the right if hsize is even.

vsize :

Vertical size of gathered area. The area is centered around each sample if vsize is odd, it extends one pixel more down if vsize is even.

average :

TRUE to divide resulting sums by the number of involved samples to get averages instead of sums.

col :

Upper-left column coordinate.

row :

Upper-left row coordinate.

width :

Area width (number of columns).

height :

Area height (number of rows).

gwy_data_field_convolve ()

void                gwy_data_field_convolve             (GwyDataField *data_field,
                                                         GwyDataField *kernel_field);

Convolves a data field with given kernel.

data_field :

A data field to convolve. It must be at least as large as 1/3 of kernel_field in each dimension.

kernel_field :

Kenrel field to convolve data_field with.

gwy_data_field_area_convolve ()

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.

data_field :

A data field to convolve. It must be at least as large as 1/3 of kernel_field in each dimension.

kernel_field :

Kenrel field to convolve data_field with.

col :

Upper-left column coordinate.

row :

Upper-left row coordinate.

width :

Area width (number of columns).

height :

Area height (number of rows).

gwy_data_field_convolve_1d ()

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_field in the corresponding dimension.

kernel_line :

Kenrel line to convolve data_field with.

orientation :

Filter orientation (see gwy_data_field_area_convolve_1d()).

Since 2.4


gwy_data_field_area_convolve_1d ()

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_field in the corresponding dimension.

kernel_line :

Kernel line to convolve data_field with.

orientation :

Filter orientation (GWY_ORIENTATION_HORIZONTAL for row-wise convolution, GWY_ORIENTATION_VERTICAL for column-wise convolution).

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


gwy_data_field_filter_median ()

void                gwy_data_field_filter_median        (GwyDataField *data_field,
                                                         gint size);

Filters a data field with median filter.

data_field :

A data field to apply the filter to.

size :

Size of area to take median of.

gwy_data_field_area_filter_median ()

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.

data_field :

A data field to apply the filter to.

size :

Size of area to take median of.

col :

Upper-left column coordinate.

row :

Upper-left row coordinate.

width :

Area width (number of columns).

height :

Area height (number of rows).

gwy_data_field_filter_mean ()

void                gwy_data_field_filter_mean          (GwyDataField *data_field,
                                                         gint size);

Filters a data field with mean filter of size size.

data_field :

A data field to apply the filter to.

size :

Averaged area size.

gwy_data_field_area_filter_mean ()

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.

data_field :

A data field to apply the filter to.

size :

Averaged area size.

col :

Upper-left column coordinate.

row :

Upper-left row coordinate.

width :

Area width (number of columns).

height :

Area height (number of rows).

gwy_data_field_filter_conservative ()

void                gwy_data_field_filter_conservative  (GwyDataField *data_field,
                                                         gint size);

Filters a data field with conservative denoise filter.

data_field :

A data field to apply the filter to.

size :

Filtered area size.

gwy_data_field_area_filter_conservative ()

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.

data_field :

A data field to apply the filter to.

size :

Filtered area size.

col :

Upper-left column coordinate.

row :

Upper-left row coordinate.

width :

Area width (number of columns).

height :

Area height (number of rows).

gwy_data_field_filter_laplacian ()

void                gwy_data_field_filter_laplacian     (GwyDataField *data_field);

Filters a data field with Laplacian filter.

data_field :

A data field to apply the filter to.

gwy_data_field_area_filter_laplacian ()

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.

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).

gwy_data_field_filter_laplacian_of_gaussians ()

void                gwy_data_field_filter_laplacian_of_gaussians
                                                        (GwyDataField *data_field);

Filters a data field with Laplacian of Gaussians filter.

data_field :

A data field to apply the filter to.

Since 2.23


gwy_data_field_area_filter_laplacian_of_gaussians ()

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


gwy_data_field_filter_sobel ()

void                gwy_data_field_filter_sobel         (GwyDataField *data_field,
                                                         GwyOrientation orientation);

Filters a data field with a directional Sobel filter.

data_field :

A data field to apply the filter to.

orientation :

Filter orientation.

gwy_data_field_area_filter_sobel ()

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.

data_field :

A data field to apply the filter to.

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).

gwy_data_field_filter_sobel_total ()

void                gwy_data_field_filter_sobel_total   (GwyDataField *data_field);

Filters a data field with total Sobel filter.

data_field :

A data field to apply the filter to.

Since 2.31


gwy_data_field_filter_prewitt ()

void                gwy_data_field_filter_prewitt       (GwyDataField *data_field,
                                                         GwyOrientation orientation);

Filters a data field with Prewitt filter.

data_field :

A data field to apply the filter to.

orientation :

Filter orientation.

gwy_data_field_area_filter_prewitt ()

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.

data_field :

A data field to apply the filter to.

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).

gwy_data_field_filter_prewitt_total ()

void                gwy_data_field_filter_prewitt_total (GwyDataField *data_field);

Filters a data field with total Prewitt filter.

data_field :

A data field to apply the filter to.

Since 2.31


gwy_data_field_filter_dechecker ()

void                gwy_data_field_filter_dechecker     (GwyDataField *data_field);

Filters a data field with 5x5 checker pattern removal filter.

data_field :

A data field to apply the filter to.

Since 2.1


gwy_data_field_area_filter_dechecker ()

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


gwy_data_field_filter_gaussian ()

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


gwy_data_field_area_filter_gaussian ()

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


gwy_data_field_filter_minimum ()

void                gwy_data_field_filter_minimum       (GwyDataField *data_field,
                                                         gint size);

Filters a data field with minimum filter.

data_field :

A data field to apply minimum filter to.

size :

Neighbourhood size for minimum search.

gwy_data_field_area_filter_minimum ()

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.

data_field :

A data field to apply minimum filter to.

size :

Neighbourhood size for minimum search.

col :

Upper-left column coordinate.

row :

Upper-left row coordinate.

width :

Area width (number of columns).

height :

Area height (number of rows).

gwy_data_field_filter_maximum ()

void                gwy_data_field_filter_maximum       (GwyDataField *data_field,
                                                         gint size);

Filters a data field with maximum filter.

data_field :

A data field to apply maximum filter to.

size :

Neighbourhood size for maximum search.

gwy_data_field_area_filter_maximum ()

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.

data_field :

A data field to apply maximum filter to.

size :

Neighbourhood size for maximum search.

col :

Upper-left column coordinate.

row :

Upper-left row coordinate.

width :

Area width (number of columns).

height :

Area height (number of rows).

gwy_data_field_filter_rms ()

void                gwy_data_field_filter_rms           (GwyDataField *data_field,
                                                         gint size);

Filters a data field with RMS filter.

data_field :

A data field to apply RMS filter to.

size :

Area size.

gwy_data_field_area_filter_rms ()

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.

data_field :

A data field to apply RMS filter to.

size :

Area size.

col :

Upper-left column coordinate.

row :

Upper-left row coordinate.

width :

Area width (number of columns).

height :

Area height (number of rows).

gwy_data_field_filter_kuwahara ()

void                gwy_data_field_filter_kuwahara      (GwyDataField *data_field);

Filters a data field with Kuwahara filter.

data_field :

A data field to apply Kuwahara filter to.

gwy_data_field_area_filter_kuwahara ()

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.

data_field :

A data filed to apply Kuwahara filter to.

col :

Upper-left column coordinate.

row :

Upper-left row coordinate.

width :

Area width (number of columns).

height :

Area height (number of rows).

gwy_data_field_filter_canny ()

void                gwy_data_field_filter_canny         (GwyDataField *data_field,
                                                         gdouble threshold);

Filters a rectangular part of a data field with canny edge detector filter.

data_field :

A data field to apply the filter to.

threshold :

Slope detection threshold (range 0..1).

gwy_data_field_shade ()

void                gwy_data_field_shade                (GwyDataField *data_field,
                                                         GwyDataField *target_field,
                                                         gdouble theta,
                                                         gdouble phi);

Shades a data field.

data_field :

A data field.

target_field :

A data field to put the shade to. It will be resized to match data_field.

theta :

Shading angle (in radians, from north pole).

phi :

Shade orientation in xy plane (in radians, counterclockwise).

gwy_data_field_filter_harris ()

void                gwy_data_field_filter_harris        (GwyDataField *x_gradient,
                                                         GwyDataField *y_gradient,
                                                         GwyDataField *result,
                                                         gint neighbourhood,
                                                         gdouble alpha);