在vtk中将PNG图像数据作为纹理投影到平面上

Question

我一直在尝试在 Python 中将图像可视化为 VTK 中平面上的部分半透明纹理。

我的方法是使用

vtkThresholdTextureCoords()

根据图像值设置透明度。 但是，我正在努力应用该阈值。 错误消息指出

texture threshold

没有标量数据。

这是代码片段：

from vtkmodules.vtkIOImage import vtkImageReader2Factory
from vtkmodules.vtkRenderingCore import (
    vtkActor,
    vtkPolyDataMapper,
    vtkRenderWindow,
    vtkRenderWindowInteractor,
    vtkRenderer,
    vtkTexture
)
from vtkmodules.vtkFiltersSources import vtkPlaneSource
from vtkmodules.vtkFiltersTexture import vtkThresholdTextureCoords
from vtkmodules.vtkCommonColor import vtkNamedColors


import vtk

def main():
    #fileName = get_program_parameters()
    fileName = 'ice.png'


    readerFactory = vtkImageReader2Factory()
    textureFile = readerFactory.CreateImageReader2(fileName)
    textureFile.SetFileName(fileName)
    textureFile.Update()


    texture = vtkTexture()
    texture.SetInputConnection(textureFile.GetOutputPort())
    texture.InterpolateOn()


    plane = vtkPlaneSource()
    plane.SetCenter(0.0,0.0,0.0)
    plane.SetNormal(0.0,1.0,0.0)

    texturePlane = vtk.vtkTextureMapToPlane()
    texturePlane.SetInputConnection(plane.GetOutputPort())
    


    thresh = vtkThresholdTextureCoords()
    thresh.SetInputConnection(texturePlane.GetOutputPort())
    thresh.ThresholdByUpper(0.1)




    planeMapper = vtkPolyDataMapper()
    planeMapper.SetInputConnection(thresh.GetOutputPort())
    #planeMapper.SetInputConnection(plane.GetOutputPort()) # This does work
    planeMapper.SetScalarRange(textureFile.GetOutput().GetScalarRange())

    planeActor = vtkActor()
    planeActor.SetMapper(planeMapper)
    planeActor.SetTexture(texture)




    # Create the RenderWindow, Renderer and Interactor.
    renderer = vtkRenderer()
    renWin = vtkRenderWindow()
    renWin.AddRenderer(renderer)
    iren = vtkRenderWindowInteractor()
    iren.SetRenderWindow(renWin)

    # Add the actors to the renderer, set the background and size.
    renderer.AddActor(planeActor)
    colors = vtkNamedColors()
    renderer.SetBackground(colors.GetColor3d('DarkSlateGray'))

    renWin.SetSize(640, 480)
    renWin.SetWindowName('TexturePlane')

    # render the image
    renWin.Render()

    renderer.ResetCamera()
    renderer.GetActiveCamera().Elevation(-30)
    renderer.GetActiveCamera().Roll(-20)
    renderer.ResetCameraClippingRange()
    renWin.Render()
    iren.Start()




    return

Answer 1

我想出了一个方法，通过设置每个像素的第四个标量值（即alpha值）。

    reader = vtk.vtkPNGReader()
    reader.SetFileName('ice.png')
    reader.Update()


    img = reader.GetOutput()

    ext = img.GetExtent()
    for y in range(ext[2],ext[3]):
        for x in range(ext[0],ext[1]):
            val0 = img.GetScalarComponentAsFloat(x,y,0,0)                
            val1 = img.GetScalarComponentAsFloat(x,y,0,1)
            val2 = img.GetScalarComponentAsFloat(x,y,0,2)
            if val0+val1+val2 < 2.:# Apply a threshold.
                                   # In this example, simply
                                   # the sum of the three
                                   # color components
                # Setting the 4th (alpha) value to zero
                img.SetScalarComponentFromFloat(x,y,0,3,0)

                        
    texture = vtkTexture()
    texture.SetInputDataObject(img)