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44 lines
2.1 KiB
Markdown
44 lines
2.1 KiB
Markdown
# Example (JKQTPlotter): QImage as a Graph {#JKQTPlotterImagePlotQImageRGB}
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This project (see `./examples/rgbimageplot_qt/`) simply creates a JKQTPlotter widget (as a new window) and adds an image plot with an image taken from a [QImage](http://doc.qt.io/qt-5/qimage.html) object.
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The source code of the main application is (see [`rgbimageplot_qt.cpp`](https://github.com/jkriege2/JKQtPlotter/tree/master/examples/rgbimageplot_qt/rgbimageplot_qt.cpp). the main parts are:
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```.cpp
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// 2. now we open a BMP-file and load it into an OpenCV cv::Mat
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QImage image(":/example.bmp");
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// 3. create a graph (JKQTPImage) with a pointer to the QImage-object, generated above
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JKQTPImage* graph=new JKQTPImage(&plot);
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graph->setTitle("");
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// copy the image into the graph (optionally you could also give a pointer to a QImage,
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// but then you need to ensure that the QImage is available as long as the JKQTPImage
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// instace lives)
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graph->setImage(image);
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// where does the image start in the plot, given in plot-axis-coordinates (bottom-left corner)
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graph->setX(0);
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graph->setY(0);
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// width/height of the image in plot coordinates
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graph->setWidth(image.width());
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graph->setHeight(image.height());
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// 4. add the graphs to the plot, so it is actually displayed
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plot.addGraph(graph);
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```
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The result looks like this:
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The image is 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).
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You can modify the program above to display the image in the correct orientation, by adding the line
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```.cpp
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// 6.1 invert y-axis, so image is oriented correctly
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plot.getYAxis()->setInverted(true);
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```
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This will reorient the y-axis to point from top to bottom (for increasing positive coordinates):
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