IDL Plot函数绘制散点图时设置透明度

目标：

如图1散点图中如果点数太多，簇与簇之间的混淆则难以辨识。因而，希望通过更改某一类簇的透明度来清晰表现不同类簇之间的混淆性与可分性。

图1 散点图

IDL中PLOT函数的关键字：

Syntax

---

graphic = PLOT(Y, [Format] [, Keywords=value] [, Properties=value])

graphic = PLOT(X, Y, [Format] [, Keywords=value] [, Properties=value])

graphic = PLOT(Equation, [Format] [, Keywords=value] [, Properties=value])

Keywords

Keywords are applied only during the initial creation of the graphic.

AXIS_STYLE=value

/BUFFER, /CURRENT, /DEVICE, DIMENSIONS=[width, height], LAYOUT=array, LOCATION=[x, y], MARGIN=scalar or [left, bottom, right, top], /NO_TOOLBAR, /NODATA, /OVERPLOT, /WIDGETS

Properties

Properties can be set as keywords to the function during creation, or retrieved or changed using the "." notation after creation.

ANTIALIAS, ASPECT_RATIO, AXES, BACKGROUND_COLOR, BACKGROUND_TRANSPARENCY, CLIP, COLOR, CROSSHAIR, EQN_SAMPLES, EQN_USERDATA, EQUATION, FILL_BACKGROUND, FILL_COLOR, FILL_LEVEL, FILL_TRANSPARENCY, FONT_COLOR, FONT_NAME, FONT_SIZE, FONT_STYLE, HIDE, HISTOGRAM, LINESTYLE, MAPGRID, MAPPROJECTION, MAP_PROJECTION, MAX_VALUE, MIN_VALUE, NAME, POSITION, RGB_TABLE, STAIRSTEP, SYM_COLOR, SYM_FILLED, SYM_FILL_COLOR, SYM_INCREMENT, SYM_OBJECT, SYM_SIZE, SYM_THICK, SYM_TRANSPARENCY, SYMBOL, THICK, TITLE, TRANSPARENCY, UVALUE, VERT_COLORS, WINDOW, WINDOW_TITLE, XRANGE, YRANGE, ZVALUE

参数有很多，与目标相关的参数为SYM_TRANSPARENCY，范围为0-100。其中，默认值为0，即不透明，100为完全透明。

SYM_TRANSPARENCY

An integer between 0 and 100 that specifies the percent transparency of the symbols. The default value is 0.

Reference:

http://www.harrisgeospatial.com/docs/PLOT.html#SYM_TRAN