JKQTPlotter trunk/v5.0.0
an extensive Qt5+Qt6 Plotter framework (including a feature-richt plotter widget, a speed-optimized, but limited variant and a LaTeX equation renderer!), written fully in C/C++ and without external dependencies
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Example (JKQTPlotter): Simple math image plot, showing a 3-channel CImg image

This project (see ./examples/rgbimageplot_cimg/) simply creates a JKQTPlotter widget (as a new window) and shows an RGB image read from a BMP-file. The image is generated as an cimg cimg_library::CImg<uint8_t> image and then copied into a single column of the internal datastore (JKQTPMathImage could be directly used without the internal datastore). To copy the data a special cimg Interface function JKQTPCopyCImgToColumn() is used, that copies the data from a CImg cimg_library::CImg<uint8_t> directly into a column.

The function JKQTPCopyCImgToColumn() is available from the (non-default) header-only extension from jkqtplotter/jkqtpinterfacecimg.h. This header provides facilities to interface JKQTPlotter with cimg. The cimg-binding itself is header-only, and NOT compiled into the JKQtPlotter libraries. Therefore you can simply include the header and use the facilities provided by it.

The CMake-build system of JKQtPlotter (and its examples) provides facilities to allow for find_package(CImg) to compile against that library. If you want to build the CImg-based JKQtPlotter examples (see list above), you either have to ensure that CMake finds CImg by itself (i.e. somewhere in the default search paths, e.g. CMAKE_INSTALL_PREFIX), or you can set the CMake variable CImg_DIR so it points to the directory of the CImg.h file, or before configuring JKQtPlotter.

The source code of the main application is (see rgbimageplot_cimg.cpp:

#include <QApplication>
#include <cmath>
#include "jkqtplotter/jkqtplotter.h"
#include "jkqtplotter/graphs/jkqtpscatter.h"
#include "jkqtplotter/graphs/jkqtpimagergb.h"
#include "jkqtplotter/jkqtpinterfacecimg.h"
#include "CImg.h"
int main(int argc, char* argv[])
{
QApplication app(argc, argv);
// 1. create a plotter window and get a pointer to the internal datastore (for convenience)
plot.getPlotter()->setUseAntiAliasingForGraphs(true); // nicer (but slower) plotting
plot.getPlotter()->setUseAntiAliasingForSystem(true); // nicer (but slower) plotting
plot.getPlotter()->setUseAntiAliasingForText(true); // nicer (but slower) text rendering
// 2. now we open a BMP-file and load it into an cimg cv::Mat
cimg_library::CImg<uint8_t> picture; // CImg<T>-Image for the data
picture.load_bmp("rgbimageplot_cimg_example.bmp");
qDebug()<<picture.width()<<"x"<<picture.height()<<"x"<<picture.spectrum();
// 3. make data available to JKQTPlotter by adding it to the internal datastore.
// In this step the contents of each channel of the cimg cv::Mat is copied into a column
// of the datastore in row-major order
size_t cPictureR=JKQTPCopyCImgToColumn(ds, picture, "R-channel", 0);
size_t cPictureG=JKQTPCopyCImgToColumn(ds, picture, "G-channel", 1);
size_t cPictureB=JKQTPCopyCImgToColumn(ds, picture, "B-channel", 2);
// 4. create a graph (JKQTPColumnRGBMathImage) with the columns created above as data
graph->setTitle("");
// where does the image start in the plot, given in plot-axis-coordinates (bottom-left corner)
graph->setX(0);
graph->setY(0);
// width and height of the image in plot-axis-coordinates
graph->setWidth(picture.width());
graph->setHeight(picture.height());
// image column with the data
graph->setImageRColumn(static_cast<int>(cPictureR));
graph->setImageGColumn(static_cast<int>(cPictureG));
graph->setImageBColumn(static_cast<int>(cPictureB));
// determine min/max of each channel manually
graph->setImageMinR(0);
graph->setImageMaxR(255);
graph->setImageMinG(0);
graph->setImageMaxG(255);
graph->setImageMinB(0);
graph->setImageMaxB(255);
// 5. add the graphs to the plot, so it is actually displayed
plot.addGraph(graph);
// 6. set axis labels
plot.getXAxis()->setAxisLabel("x [pixels]");
plot.getYAxis()->setAxisLabel("y [pixels]");
// 6.1 invert y-axis, so image is oriented correctly
plot.getYAxis()->setInverted(true);
// 7. fix axis aspect ratio to width/height, so pixels are square
plot.getPlotter()->setAspectRatio(double(picture.width())/double(picture.height()));
// 8. autoscale the plot so the graph is contained
plot.zoomToFit();
// show plotter and make it a decent size
plot.show();
plot.resize(800,600);
plot.setWindowTitle("JKQTPColumnRGBMathImage");
return app.exec();
}
void setAspectRatio(double __value)
sets the data aspect ratio, enforced with setMaintainApsectRatio(true)
void setMaintainAspectRatio(bool value)
en-/disables the maintaining of the data aspect ratio
void setUseAntiAliasingForSystem(bool __value)
specifies whether to use antialiasing for plotting the coordinate system
void setUseAntiAliasingForGraphs(bool __value)
specifies whether to use antialiasing for plotting the graphs
void setUseAntiAliasingForText(bool __value)
specifies whether to use antialiasing when drawing any text
like JKQTPRGBMathImage but reads images from columns of the datastore
Definition jkqtpimagergb.h:490
virtual void setImageBColumn(int __value)
image column for B channel
virtual void setImageRColumn(int __value)
image column for R channel
virtual void setImageGColumn(int __value)
image column for G channel
void setAxisLabel(const QString &__value)
axis label of the axis
void setInverted(bool __value)
indicates whether the axis is to be inverted or not
This class manages data columns (with entries of type double ), used by JKQTPlotter/JKQTBasePlotter t...
Definition jkqtpdatastorage.h:282
void setHeight(double __value)
height of image
void setX(double __value)
x coordinate of lower left corner
void setWidth(double __value)
width of image
void setY(double __value)
y coordinate of lower left corner
void setImageMaxR(double m)
red image value range maximum
void setImageMaxG(double __value)
green image value range maximum
virtual void setTitle(const QString &title) override
sets the title of the plot (for display in key!).
void setImageMinB(double __value)
blue image value range minimum
void setImageMinR(double m)
red image value range minimum
void setImageMinG(double __value)
green image value range minimum
void setImageMaxB(double __value)
blue image value range maximum
plotter widget for scientific plots (uses JKQTBasePlotter to do the actual drawing)
Definition jkqtplotter.h:364
void zoomToFit(bool zoomX=true, bool zoomY=true, bool includeX0=false, bool includeY0=false, double scaleX=1.05, double scaleY=1.05)
this method zooms the graph so that all plotted datapoints are visible.
Definition jkqtplotter.h:1039
JKQTPVerticalAxisBase * getYAxis(JKQTPCoordinateAxisRef axis=JKQTPPrimaryAxis)
returns the y-axis objet of the plot
Definition jkqtplotter.h:713
JKQTBasePlotter * getPlotter()
returns the JKQTBasePlotter object internally used for plotting
Definition jkqtplotter.h:404
size_t addGraph(JKQTPPlotElement *gr)
Definition jkqtplotter.h:784
JKQTPDatastore * getDatastore()
returns a pointer to the datastore used by this object
Definition jkqtplotter.h:611
JKQTPHorizontalAxisBase * getXAxis(JKQTPCoordinateAxisRef axis=JKQTPPrimaryAxis)
returns the x-axis objet of the plot
Definition jkqtplotter.h:711
size_t JKQTPCopyCImgToColumn(JKQTPDatastore *datastore, const cimg_library::CImg< T > &img, const QString &name=QString(""), int channel=0, int z=0)
add one external column to the datastore. It will be filled with the contents of the CImg image img.
Definition jkqtpinterfacecimg.h:42

The result looks like this:

imageplot

Note the step

// 5.1 invert y-axis, so image is oriented correctly
plot.getYAxis()->setInverted(true);

above, which ensures that the image is not draw upside-down! This will reorient the y-axis to point from top to bottom (for increasing positive coordinates). The image would be upside-down, because computer images use a coordinate system with 0 at the top-left (left-handed coordinate system) and the JKQTPlotter has its 0 at the bottom-left (right-handed coordinate system).

See examples/rgbimageplot for a detailed description of the other possibilities that the class JKQTPColumnRGBMathImage offer with respect to determining how an image is plotted.