Pixbuf rendering: Gwyddion Widgets Library Reference Manual

Pixbuf rendering

Pixbuf rendering — Draw GwyDataFields to GdkPixbufs

Functions

void	gwy_draw_data_field_pixbuf_full ()
void	gwy_draw_data_field_pixbuf_with_range ()
void	gwy_draw_data_field_pixbuf_adaptive ()
void	gwy_map_data_field_adaptive ()
void	gwy_draw_data_field_pixbuf ()
void	gwy_draw_data_field_pixbuf_mask ()

Types and Values

enum	GwyColorMappingType

Includes

#include <libgwyui/gwyui.h>

Description

The simpliest method to render a GwyDataField to a GdkPixbuf with a false colour scale is gwy_draw_data_field_pixbuf_full() which uniformly stretches the colour gradient from value minimum to maximum. Functions gwy_draw_data_field_pixbuf_with_range() and gwy_draw_data_field_pixbuf_adaptive() offer other false colour mapping possibilities. A bit different is gwy_draw_data_field_pixbuf_mask() which represents the values as opacities of a single colour.

Functions

gwy_draw_data_field_pixbuf_full()

void
gwy_draw_data_field_pixbuf_full (GdkPixbuf *pixbuf,
                                 GwyDataField *data_field,
                                 GwyGradient *gradient);

Renders a data field to a pixbuf with an auto-stretched colour gradient.

Minimum data value is mapped to start of gradient , maximum value to its end, values between are mapped linearly to gradient .

Parameters

pixbuf	A Gdk pixbuf to draw to.	[transfer none]
data_field	A data field to draw.	[transfer none]
gradient	A colour gradient to draw with.	[transfer none]

gwy_draw_data_field_pixbuf_with_range()

void
gwy_draw_data_field_pixbuf_with_range (GdkPixbuf *pixbuf,
                                       GwyDataField *data_field,
                                       GwyGradient *gradient,
                                       gdouble minimum,
                                       gdouble maximum);

Renders a data field to a pixbuf with an explicit colour gradient range.

minimum and all smaller values are mapped to start of gradient , maximum and all greater values to its end, values between are mapped linearly to gradient .

Parameters

pixbuf	A Gdk pixbuf to draw to.	[transfer none]
data_field	A data field to draw.	[transfer none]
gradient	A colour gradient to draw with.	[transfer none]
minimum	The value corresponding to gradient start.
maximum	The value corresponding to gradient end.

gwy_draw_data_field_pixbuf_adaptive()

void
gwy_draw_data_field_pixbuf_adaptive (GdkPixbuf *pixbuf,
                                     GwyDataField *data_field,
                                     GwyGradient *gradient);

Renders a data field to a pixbuf with a colour gradient adaptively.

The mapping from data field (minimum, maximum) range to gradient is nonlinear, deformed using inverse function to height density cummulative distribution.

Parameters

pixbuf	A Gdk pixbuf to draw to.	[transfer none]
data_field	A data field to draw.	[transfer none]
gradient	A colour gradient to draw with.	[transfer none]

gwy_map_data_field_adaptive()

void
gwy_map_data_field_adaptive (GwyDataField *data_field,
                             const gdouble *z,
                             gdouble *mapped,
                             guint n);

Maps ordinate values to interval [0,1] as gwy_draw_data_field_pixbuf_adaptive() would do.

This is useful to find out which positions in the false colour gradient correspond to specific values.

Parameters

data_field	A data field to draw.	[transfer none]
z	Array of `n` data values to map.
mapped	Output array of size `n` where mapped `z` values are to be stored.
n	Number of elements in `z` and `mapped` .

gwy_draw_data_field_pixbuf()

void
gwy_draw_data_field_pixbuf (GdkPixbuf *pixbuf,
                            GwyDataField *data_field,
                            GwyGradient *gradient,
                            GwyColorMappingType mapping,
                            gdouble *minimum,
                            gdouble *maximum);

Renders a data field to a pixbuf in specified mapping mode.

The minimum and maximum arguments input values are used only in GWY_COLOR_MAPPING_FIXED mode. They must not be NULL in such case.

In all modes, the actual mapping start and end will be returned in minimum and maximum if they are not NULL. In GWY_COLOR_MAPPING_FIXED mode the range is simply preserved.

Parameters

pixbuf	A Gdk pixbuf to draw to.	[transfer none]
data_field	A data field to draw.	[transfer none]
gradient	A colour gradient to draw with.	[transfer none]
mapping	False colour mapping type.
minimum	The value corresponding to gradient start.	[inout]
maximum	The value corresponding to gradient end.	[inout]

gwy_draw_data_field_pixbuf_mask()

void
gwy_draw_data_field_pixbuf_mask (GdkPixbuf *pixbuf,
                                 GwyDataField *data_field,
                                 const GwyRGBA *color);

Renders a data field to a pixbuf as a single-colour mask with varying opacity.

Values equal or smaller to 0.0 are drawn as fully transparent, values greater or equal to 1.0 as fully opaque, values between are linearly mapped to pixel opacity.

Parameters

pixbuf	A Gdk pixbuf to draw to.	[transfer none]
data_field	A data field to draw.	[transfer none]
colour	A colour to use.

Types and Values

enum GwyColorMappingType

Types of false colour gradient mapping in GwyDataView.

Members

GWY_COLOR_MAPPING_FULL	Colour gradient is uniformly mapped to range from data minimum to maximum.
GWY_COLOR_MAPPING_FIXED	Colour gradient is uniformly mapped to a fixed range, independent on data.
GWY_COLOR_MAPPING_AUTO	Colour gradient is uniformly mapped to a range inside which most of data points lie, that is height distribution tails are cut off.
GWY_COLOR_MAPPING_ADAPT	Colour gradient is mapped nonuniformly, see `gwy_draw_data_field_pixbuf_adaptive()`.