ImageText
VTKExamples/Cxx/Images/ImageText
Description¶
This example demonstrates how to draw text onto an image vtkImageData. It uses vtkImageBlend to blend the text and the image. For another example using vtkImageBlend, see CombineImages.
Seealso
DrawText for an example of drawing text, also in 2D, but into the render window rather than into a vtkImageData object.
Code¶
ImageText.cxx
#include <vtkImageBlend.h> #include <vtkImageData.h> #include <vtkPointData.h> #include <vtkPNGWriter.h> #include <vtkSmartPointer.h> #include <vtkFreeTypeUtilities.h> #include <vtkTextProperty.h> #include <vtkImageCanvasSource2D.h> // must build VTK with VTK_USE_SYSTEM_FREETYPE=ON int main(int argc, char* argv[]) { // Create a black image with a red circle of radius 50 centered at (60, 60) vtkSmartPointer<vtkImageCanvasSource2D> drawing = vtkSmartPointer<vtkImageCanvasSource2D>::New(); drawing->SetScalarTypeToUnsignedChar(); // PNGWriter requires unsigned char (or unsigned short) drawing->SetNumberOfScalarComponents(3); drawing->SetExtent(0, 150, 0, 120, 0, 0); // xmin, xmax, ymin, ymax, zmin, zmax drawing->SetDrawColor(255, 0, 0); // red drawing->DrawCircle(60, 60, 50); // parameters: x, y, radius // Create an image of text vtkSmartPointer<vtkFreeTypeUtilities> freeType = vtkSmartPointer<vtkFreeTypeUtilities>::New(); vtkSmartPointer<vtkTextProperty> textProperty = vtkSmartPointer<vtkTextProperty>::New(); textProperty->SetColor(1.0, 1.0, 0.0); // yellow textProperty->SetFontSize(24); vtkSmartPointer<vtkImageData> textImage = vtkSmartPointer<vtkImageData>::New(); freeType->RenderString(textProperty, "Test String", textImage); // Combine the images vtkSmartPointer<vtkImageBlend> blend = vtkSmartPointer<vtkImageBlend>::New(); blend->AddInputConnection(drawing->GetOutputPort()); blend->AddInputData(textImage); blend->SetOpacity(0, 0.5); // background image: 50% opaque blend->SetOpacity(1, 1.0); // text: 100% opaque blend->Update(); vtkSmartPointer<vtkPNGWriter> writer = vtkSmartPointer<vtkPNGWriter>::New(); writer->SetFileName("output.png"); writer->SetInputConnection(blend->GetOutputPort()); writer->Write(); return EXIT_SUCCESS; }
CMakeLists.txt¶
cmake_minimum_required(VERSION 2.8) PROJECT(ImageText) find_package(VTK REQUIRED) include(${VTK_USE_FILE}) add_executable(ImageText MACOSX_BUNDLE ImageText.cxx) target_link_libraries(ImageText ${VTK_LIBRARIES})
Download and Build ImageText¶
Danger
The generation of tar files has not been ported to the new VTKExamples. Some tarballs may be missing or out-of-date.
Click here to download ImageText and its CMakeLists.txt file. Once the tarball ImageText.tar has been downloaded and extracted,
cd ImageText/build
If VTK is installed:
cmake ..
If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:
cmake -DVTK_DIR:PATH=/home/me/vtk_build ..
Build the project:
make
and run it:
./ImageText
WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.