This method uses spline function to modifiy the YCrCb values of a raster image.
Parameters
| Name | Explanation |
|---|---|
| x | An array of x coordinate values defining points of a polygonal area on the image. (in pixels) * (see Note below) |
| y | An array of y coordinate values defining points of a polygonal area on the image. (in pixels) * (see Note below) |
| spx | An array of YCrCb values defining the x coordinates of points on the YCCSplineVariant curve. (from 0 to 255) ** |
| spy | An array of YCrCb values defining the y coordinates of points on the YCCSplineVariant curve. (from 0 to 255) ** |
| spPoints | The number of (spx, spy) coordinates in the array (from 3 to 10) |
| Yb | Affects the Y component (luminance) of the YCrCb value (False(0): does not affect the Y component, True( nonzero): affects the Y component) |
| Cr | Affects the Cr component (chrominance) of the YCrCb value (False(0): does not affect the Cr component, True( nonzero): affects the Cr component) |
| Cb | Affects the Cb component (chrominance) of the YCrCb value (False(0): does not affect the Cb component, True( nonzero): affects the Cb component) |
| * NOTE for retrieving array values: In Visual Basic / VB.NET, if the array is defined as Dim x(0 To 2), then the arguments are returned in x. In C#.NET the arguments are returned in ref x. |
|
Return Value
Returns True (nonzero) if successful, otherwise returns False (0).
Explanation
The YCCSplineVariant method uses a spline function to modify the YCrCb values of a raster image. A spline function is a method of interpolating values that lay in between data points. In other words it produces a smooth curve from a limited set of points.
This method is recommended when using scripting or other languages that require variant types or when using 64 bit builds in VB.NET or C#.
The YCCSplineVariant method allows you to define the relationship between the input YCrCb values in the original image and output YCrCb values in the newly created image. You do this by specifying a set of coordinate points where the input YCrCb values are the x coordinates and the output YCrCb values are the y coordinates. These coordinate points are stored in arrays and passed to the YCCSplineVariant method through the spx and spy parameters. The YCCSplineVariant method then interpolates a "smooth" curve from these coordinate points. The graphic representation of this relationship between input YCrCb and output YCrCb values is known as the YCCSplineVariant curve. A sample YCCSplineVariant curve is shown in the diagram below:
In the above diagram, the Cr default YCCSplineVariant curve represents no change between input YCrCb values and output YCrCb values. In this case, the newly created image is exactly the same as the orginal image. The red YCCSplineVariant curve represents an increase in contrast between the original image and the newly created image. It was generated from the following points:
Point (spx
values,spy values)
-----------------------------------------------------
Point
A (0,0)
Point
B (64,32)
Point
C (128,128)
Point
D (192,160)
Point
E (255,255)
At the midpoint of the Yb YCCSplineVariant curve, the input YCrCb value of 128 equals the output YCrCb value of 128. At points below the midpoint, however, the output YCrCb values are lower than the input YCrCb values. This means that dark colors become darker. Conversely, at points above the midpoint, output YCrCb values are higher than input YCrCb values. This means that light colors become lighter. This particular YCCSplineVariant curve therefore increases the contrast of the image.
An YCCSplineVariant curve that decreases contrast could be defined with the following points:
Point (spx
values,spy values)
----------------------------------------------------
Point
A (0,0)
Point
B (64, 96)
Point
C (128,128)
Point
D (225, 192)
Point
E (255,255)
To execute the YCCSplineVariant method, set the image handle of the image in the ImageHandle property or the Layer(LayerNo).ImageHandle property. The YCCSplineVariant method supports 1, 4, 8, 16, 24, and 32 bit images.
Before executing the YCCSplineVariant method, you must set the area on the image that will be affected. There are 4 ways to do this.
- To use a mask image, set the SelectMode property to 0. Set the mask image handle in the MaskImageHandle property
- To process the total image, set the SelectMode property to 1
- To process the polygonal area on the image, set the SelectMode property to 2. Select the polygon by setting the appropriate coordinate values for the points of the polygon in two arrays, one array for the x coordinate values and one array for the y coordinate values. The pass these arrays to the x and y arguments of the YCCSplineVariant method. The number of points defining the polygon must be 3 or more
- To process an elliptical area on the image, set the SelectMode property to 3. Select the ellipse by setting the appropriate values for the bounding rectangle in the RectLeft, RectTop, RectRight, and RectBottom properties
When the SelectMode
property is set to values other than 2 (ikEffectPolygon), please
set dummy arrays in the x and y parameters.
When the SelectMode property
is set to 2 or 3, the appropriate value must be set in the InOut property. When a 1, 4, or 8 bit image
is processed, the total image will be processed regardless of the
value set in the SelectMode
property.
If successful the resulting raster image data is set in the LayerNo property (the ImageHandle property or the Layer(LayerNo).ImageHandle property. If unsuccessful, 0 is returned.
When the Caption, Message, and ButtonName properties are blank, the progress dialog box will not be displayed. When the progress dialog box is displayed, the percentage that the processing has completed will be shown in the dialog box.
Also see the YCCSpline method.