ImageText
VTKExamples/Cxx/Images/ImageText
Description
This example demonstrates how to draw text onto an image ({{class|vtkImageData}}). It uses {{class|vtkImageBlend}} to blend the text and the image. For another example using vtkImageBlend, see .
See also 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
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.