WorldWind Source Analysis Series: Image Layer Class Imagelayer

Image Layer Class Imagelayer

The imagery layer class Imagelayer maps a single image to the surface of the planet as a texture. The source image must be a planar Cartesian coordinate system. The class diagram for this class is as follows.

The primary fields, properties, and methods provided by the imagery layer class Imagelayer are briefly described below:

Protected double layerradius;//the radius of the layer, actually the radius of the planet that added the image texture

protected double Minlat; Minimum latitude of a layer

protected double Maxlat; Maximum latitude of a layer

protected double Minlon; Minimum longitude of the layer

Protected maximum longitude of a double maxlon;//layer

Planet objects that are dependent on the world m_parentworld;//layer

Stream m_texturestream = Texture data stream contained by the null;//layer

protected bool _disablezbuffer;//whether to enable ZBuffer buffering for image texture layers

Protected customvertex.positionnormaltextured[] vertices;//the position coordinates of the normals and textures corresponding to the images when they are mapped to textures

protected static customvertex.transformedcolored[] Progressbaroutline = new CUSTOMVERTEX.TRANSFORMEDCOLORED[5];

protected static customvertex.transformedcolored[] ProgressBar = new Customvertex.transformedcolored[4];

Protected short[] indices;//use index cache to reduce memory usage and accelerate rendering

Protected Texture texture;//texture objects created from imagery

Protected device device;//rendering textures

protected string _imageurl; URL string for the texture image

protected string _imagepath; Path to the texture image

protected int meshpointcount = 64;//The dot density of the triangular lattice of the texture image

Protected Terrainaccessor _terrainaccessor;//image texture for terrain accessors

protected int progressbarbackcolor = SYSTEM.DRAWING.COLOR.FROMARGB (100, 255, 255, 255). ToArgb ();//Background color of progress bar

protected int progressbaroutlinecolor = SYSTEM.DRAWING.COLOR.SLATEGRAY.TOARGB ();//Outline color of progress bar

protected int textcolor = System.Drawing.Color.Black.ToArgb ();

protected float downloadpercent;//Download the percentage of arts and sciences images completed

Protected thread downloadthread;//downloading arts and sciences images

protected float verticalexaggeration;//vertical magnification of texture

Protected string m_legendimagepath;//legend image Path

protected Colorbar Legendcontrol; Color bar legend Control form

int m_transparentcolor = 0;//transparent area color

BOOL M_rendergrayscale = false;//whether grayscale rendering

TimeSpan cacheexpiration = timespan.maxvalue; buffer Expiration time period

System.Timers.Timer Refreshtimer = null;//Refresh Timer

float m_grayscalebrightness = 0.0f;//transparency of gray scale

static Effect Grayscaleeffect = null;//Enable Effect object

public override void Initialize(Drawargs Drawargs): Overloads the parent class method, creates a download thread based on the URL, creates a grid, and so on.

public override void update(Drawargs Drawargs): Overloads the parent class method to update the state based on the drawing parameters.

public override void render(Drawargs Drawargs): Overloads the parent class method to finish rendering the imagery layer based on the drawing parameters.

protected virtual void Createmesh (): Creates a collection of points required by the device to render the triangular polygon grid eventually, i.e. protected customvertex.positionnormaltextured[] Vertices, and specifies the vertex index (protected short[] indices for each vertex that makes up the triangular grid. Using both vertex and index caches, you can reduce memory usage and speed up rendering.

protected void Downloadimage (): a handler that is bound by the download thread, internally constructs the network download Webdownload object to initiate a network download, and specifies a handler for the object's downloading events in order to display the download percentage in the progress bar. Where _imagepath is empty, the downloaded file is placed in memory, and then the Imagehelper class is converted from the Stream object load to a texture object, and when _imagepath is not empty, the loaded file is saved to--imagepath, and then the update texture is loaded , and finally call Createmesh () to create the mesh.

private static string Getfilepathfromurl (string URL): Gets the file path from the URL string.

private void Calculate_normals (ref customvertex.positionnormaltextured[] vertices, short[] indices): Calculates the normals of the grid vertices, The normal is used in the light state.

WorldWind Source Analysis Series: Image Layer Class Imagelayer