SkScalar.cpp File Reference

#include "include/core/SkScalar.h"
#include "include/private/base/SkDebug.h"

Go to the source code of this file.

Functions
SkScalar	SkScalarInterpFunc (SkScalar searchKey, const SkScalar keys[], const SkScalar values[], int length)

Function Documentation

SkScalarInterpFunc()

SkScalar SkScalarInterpFunc	(	SkScalar	searchKey,
		const SkScalar	keys[],
		const SkScalar	values[],
		int	length
	)

Interpolate along the function described by (keys[length], values[length]) for the passed searchKey. SearchKeys outside the range keys[0]-keys[Length] clamp to the min or max value. This function assumes the number of pairs (length) will be small and a linear search is used.

Repeated keys are allowed for discontinuous functions (so long as keys is monotonically increasing). If key is the value of a repeated scalar in keys the first one will be used.

Definition at line 11 of file SkScalar.cpp.

                                                                 {
    SkASSERT(length > 0);
    SkASSERT(keys != nullptr);
    SkASSERT(values != nullptr);
#ifdef SK_DEBUG
    for (int i = 1; i < length; i++) {
        SkASSERT(keys[i-1] <= keys[i]);
    }
#endif
    int right = 0;
    while (right < length && keys[right] < searchKey) {
        ++right;
    }
    // Could use sentinel values to eliminate conditionals, but since the
    // tables are taken as input, a simpler format is better.
    if (right == length) {
        return values[length-1];
    }
    if (right == 0) {
        return values[0];
    }
    // Otherwise, interpolate between right - 1 and right.
    SkScalar leftKey = keys[right-1];
    SkScalar rightKey = keys[right];
    SkScalar fract = (searchKey - leftKey) / (rightKey - leftKey);
    return SkScalarInterp(values[right-1], values[right], fract);
}