2.2.2.5 EmfPlusBlendFactors Object
The EmfPlusBlendFactors object specifies positions and factors for the blend pattern of a gradient brush.
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PositionCount |
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BlendPositions (variable) |
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BlendFactors (variable) |
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PositionCount (4 bytes): An unsigned integer that specifies the number of positions in the BlendPositions field and factors in the BlendFactors field.
BlendPositions (variable): An array of PositionCount 32-bit floating-point values that specify proportions of distance along the gradient line.
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Each value MUST be a number between 0.0 and 1.0 inclusive. There MUST be at least two positions specified: the first position, which is always 0.0f, and the last position, which is always 1.0f. Each position in BlendPositions is generally greater than the preceding position. For a linear gradient brush, 0.0 represents the starting point and 1.0 represents the ending point. For a path gradient brush, 0.0 represents the midpoint and 1.0 represents an endpoint.
BlendFactors (variable): An array of PositionCount 32-bit floating-point values that specify proportions of colors at the positions defined in the BlendPositions field. Each value MUST be a number between 0.0 and 1.0 inclusive.
For a linear gradient brush, 0.0 represents 0% starting color and 100% ending color, and 1.0 represents 100% starting color and 0% ending color. For a path gradient brush, 0.0 represents 0% midpoint color and 100% endpoint color, and 1.0 represents 100% midpoint color and 0% endpoint color.
For example, if a linear gradient brush specifies a position of 0.2 and a factor of 0.3 along a gradient line that is 100 pixels long, the color that is 20 pixels along that line consists of 30 percent starting color and 70 percent ending color.
Gradient brushes are specified by EmfPlusLinearGradientBrushData objects (section 2.2.2.24) and EmfPlusPathGradientBrushData objects (section 2.2.2.29). Blend patterns are used to smoothly shade the interiors of shapes filled by gradient brushes. and can be defined by arrays of positions and colors or positions and factors. Positions and colors are specified by EmfPlusBlendColors objects (section 2.2.2.4).
An EmfPlusBlendFactors object MUST be present in the OptionalData field of an EmfPlusLinearGradientBrushData or EmfPlusPathGradientBrushData object if either of the flags BrushDataBlendFactorsH or BrushDataBlendFactorsV is set in its BrushDataFlags field.
See section 2.2.2 for the specification of additional structure objects.