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Add documentation to SkRGBA4f

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Bug: skia:
Change-Id: I11109b35558630e60118653c9c72a976bc6e4650
Reviewed-on: https://skia-review.googlesource.com/c/159151
Reviewed-by: Mike Klein <mtklein@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
This commit is contained in:
Brian Osman 2018-10-04 14:25:25 -04:00 committed by Skia Commit-Bot
parent 6edbde6248
commit 82727ad0eb
1 changed files with 103 additions and 6 deletions
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105
include/core/SkColor.h
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@ -228,59 +228,149 @@ SK_API SkPMColor SkPreMultiplyARGB(U8CPU a, U8CPU r, U8CPU g, U8CPU b);
*/
SK_API SkPMColor SkPreMultiplyColor(SkColor c);
/** \struct SkRGBA4f
RGBA color value, holding four floating point components. Color components are always in
a known order. kAT determines if the SkRGBA4f's R, G, and B components are premultiplied
by alpha or not.
Skia's public API always uses unpremultiplied colors, which can be stored as
SkRGBA4f<kUnpremul_SkAlphaType>. For convenience, this type can also be referred to
as SkColor4f.
*/
template <SkAlphaType kAT>
struct SkRGBA4f {
float fR;
float fG;
float fB;
float fA;
float fR; //!< red component
float fG; //!< green component
float fB; //!< blue component
float fA; //!< alpha component
/** Compares SkRGBA4f with other, and returns true if all components are equal.
@param other SkRGBA4f to compare
@return true if SkRGBA4f equals other
*/
bool operator==(const SkRGBA4f& other) const {
return fA == other.fA && fR == other.fR && fG == other.fG && fB == other.fB;
}
/** Compares SkRGBA4f with other, and returns true if not all components are equal.
@param other SkRGBA4f to compare
@return true if SkRGBA4f is not equal to other
*/
bool operator!=(const SkRGBA4f& other) const {
return !(*this == other);
}
/** Returns SkRGBA4f multiplied by scale.
@param scale value to multiply by
@return SkRGBA4f as (fR * scale, fG * scale, fB * scale, fA * scale)
*/
SkRGBA4f operator*(float scale) const {
return { fR * scale, fG * scale, fB * scale, fA * scale };
}
/** Returns SkRGBA4f multiplied component-wise by scale.
@param scale SkRGBA4f to multiply by
@return SkRGBA4f as (fR * scale.fR, fG * scale.fG, fB * scale.fB, fA * scale.fA)
*/
SkRGBA4f operator*(const SkRGBA4f& scale) const {
return { fR * scale.fR, fG * scale.fG, fB * scale.fB, fA * scale.fA };
}
/** Returns a pointer to components of SkRGBA4f, for array access.
@return pointer to array [fR, fG, fB, fA]
*/
const float* vec() const { return &fR; }
/** Returns a pointer to components of SkRGBA4f, for array access.
@return pointer to array [fR, fG, fB, fA]
*/
float* vec() { return &fR; }
/** Returns one component. Asserts if index is out of range and SK_DEBUG is defined.
@param index one of: 0 (fR), 1 (fG), 2 (fB), 3 (fA)
@return value corresponding to index
*/
float operator[](int index) const {
SkASSERT(index >= 0 && index < 4);
return this->vec()[index];
}
/** Returns one component. Asserts if index is out of range and SK_DEBUG is defined.
@param index one of: 0 (fR), 1 (fG), 2 (fB), 3 (fA)
@return value corresponding to index
*/
float& operator[](int index) {
SkASSERT(index >= 0 && index < 4);
return this->vec()[index];
}
/** Returns true if SkRGBA4f is an opaque color. Asserts if fA is out of range and
SK_DEBUG is defined.
@return true if SkRGBA4f is opaque
*/
bool isOpaque() const {
SkASSERT(fA <= 1.0f && fA >= 0.0f);
return fA == 1.0f;
}
/** Returns SkRGBA4f clamped to normalized range. Clamps a to [0, 1].
If SkRGBA4f is premultiplied, clamps r, g, and b to [0, fA].
If SkRGBA4f is unpremultiplied, clamps r, g, b to [0, 1].
@return clamped SkRGBA4f
*/
static SkRGBA4f Pin(float r, float g, float b, float a); // impl. depends on kAT
/** Returns SkRGBA4f clamped to normalized range. Clamps fA to [0, 1].
If SkRGBA4f is premultiplied, clamps fR, fG, and fB to [0, fA].
If SkRGBA4f is unpremultiplied, clamps fR, fG, fB to [0, 1].
@return clamped SkRGBA4f
*/
SkRGBA4f pin() const { return Pin(fR, fG, fB, fA); }
/** Returns closest SkRGBA4f to SkColor. Only allowed if SkRGBA4f is unpremultiplied.
@return SkColor as SkRGBA4f
*/
static SkRGBA4f FromColor(SkColor); // impl. depends on kAT
/** Returns closest SkColor to SkRGBA4f. Only allowed if SkRGBA4f is unpremultiplied.
@return color as SkColor
*/
SkColor toSkColor() const; // impl. depends on kAT
/** Returns closest SkRGBA4f to SkPMColor. Only allowed if SkRGBA4f is premultiplied.
@return SkPMColor as SkRGBA4f
*/
static SkRGBA4f FromPMColor(SkPMColor); // impl. depends on kAT
/** Returns SkRGBA4f premultiplied by alpha. Asserts at compile time if SkRGBA4f is
already premultiplied.
@return premultiplied color
*/
SkRGBA4f<kPremul_SkAlphaType> premul() const {
static_assert(kAT == kUnpremul_SkAlphaType, "");
return { fR * fA, fG * fA, fB * fA, fA };
}
/** Returns SkRGBA4f unpremultiplied by alpha. Asserts at compile time if SkRGBA4f is
already unpremultiplied.
@return unpremultiplied color
*/
SkRGBA4f<kUnpremul_SkAlphaType> unpremul() const {
static_assert(kAT == kPremul_SkAlphaType, "");
@ -293,7 +383,14 @@ struct SkRGBA4f {
}
};
/** \struct SkColor4f
RGBA color value, holding four floating point components. Color components are always in
a known order, and are unpremultiplied.
This is a specialization of SkRGBA4f. For details, @see SkRGBA4f.
*/
using SkColor4f = SkRGBA4f<kUnpremul_SkAlphaType>;
template <> SK_API SkColor4f SkColor4f::FromColor(SkColor);
template <> SK_API SkColor SkColor4f::toSkColor() const;