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improved readme

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jkriege2 2018-12-11 23:01:03 +01:00
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test/simpletest_impulsesplot/README.md
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@ -8,79 +8,51 @@ The soruce code of the main application is (see [`jkqtplotter_simpletest_impulse
First the data columns for three x-y-curves are generated. One column of x-values with entries 0,1,2,...,254,255 (256 entries).
First data for a curve is calculated and stored in `QVector<double`:
```c++
size_t columnX=ds->addLinearColumn(256, 0, 255, "x");
```
And three columns with 256 entries each, which will be filled with the R-, G- and B-histograms of an image `example.bmp`:
```c++
size_t columnR=ds->addColumn(256, "historam_R");
size_t columnG=ds->addColumn(256, "historam_G");
size_t columnB=ds->addColumn(256, "historam_B");
```
In this example we will access the data in the internal datastore directly. This access is possible through objects of type JKQTPcolumn, which is a proxy to the data in one of the columns in a `JKQTdatastore`:
```c++
JKQTPcolumn cG=ds->getColumn(columnG);
JKQTPcolumn cR=ds->getColumn(columnR);
JKQTPcolumn cB=ds->getColumn(columnB);
```
In order to calculate the histograms, first all entries in the columns are set to 0:
```c++
cR.setAll(0);
cG.setAll(0);
cB.setAll(0);
```
Finally the histogram is calculated:
```c++
QImage image(":/example.bmp");
for (int y=0; y<image.height(); y++) {
for (int x=0; x<image.width(); x++) {
QRgb pix=image.pixel(x,y);
cR.incValue(qRed(pix), 1);
cG.incValue(qGreen(pix), 1);
cB.incValue(qBlue(pix), 1);
QVector<double> X, Y;
for (int i=0; i<Ndata; i++) {
const double xx=double(i)/double(Ndata)*6.0*M_PI;
X << xx;
Y << cos(xx)*exp(-xx/10.0);
}
}
cR.scale(100.0/static_cast<double>(image.width()*image.height()));
cG.scale(100.0/static_cast<double>(image.width()*image.height()));
cB.scale(100.0/static_cast<double>(image.width()*image.height()));
```
Finally three `JKQTPfilledCurveXGraph` objects are generated and added to the plot (here we show the code for the R-channel only):
... and finally the data is copied into the datastore
```c++
JKQTPfilledCurveXGraph* graphR=new JKQTPfilledCurveXGraph(&plot);
// set graph titles
graphR->set_title("R-channel");
// set graph colors (lines: non-transparent, fill: semi-transparent
QColor col;
col=QColor("red"); graphR->set_color(col);
col.setAlphaF(0.25); graphR->set_fillColor(col);
// set data
graphR->set_xColumn(columnX); graphR->set_yColumn(columnR);
// add the graphs to the plot, so they are actually displayed
plot.addGraph(graphR);
size_t columnX=ds->addCopiedColumn(X, "x");
size_t columnY=ds->addCopiedColumn(Y, "y");
```
Now an impulse graph object is generated and added to the plot:
```c++
JKQTPimpulsesVerticalGraph* graph=new JKQTPimpulsesVerticalGraph(&plot);
graph->set_xColumn(columnX);
graph->set_yColumn(columnY);
graph->set_lineWidth(2);
graph->set_color(QColor("red"));
graph->set_title(QObject::tr("$\\cos(x)\\cdot\\exp(-x/10)$"));
plot.addGraph(graph);
```
The result looks like this:
![jkqtplotter_simpletest_impulsesplot](https://raw.githubusercontent.com/jkriege2/JKQtPlotter/master/screenshots/jkqtplotter_simpletest_impulsesplot.png)
There is an alternative class `JKQTPimpulsesHorizontalGraph` which draws horizontal impulse plots:
```c++
JKQTPimpulsesHorizontalGraph* graph=new JKQTPimpulsesHorizontalGraph(&plot);
graph->set_yColumn(columnX);
graph->set_xColumn(columnY);
graph->set_lineWidth(2);
graph->set_color(QColor("blue"));
graph->set_title(QObject::tr("$\\cos(x)\\cdot\\exp(-x/10)$"));
```
This code snippet results in a plot like this:
![jkqtplotter_simpletest_impulsesplot](https://raw.githubusercontent.com/jkriege2/JKQtPlotter/master/screenshots/jkqtplotter_simpletest_impulsesplot_horizontal.png)
[Back to JKQTPlotter main page](https://github.com/jkriege2/JKQtPlotter/)