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// Intrinsics that are available to public SkSL (SkRuntimeEffect)
// See "The OpenGL ES Shading Language, Section 8"
// 8.1 : Angle and Trigonometry Functions
$pure $genType radians($genType degrees);
$pure $genHType radians($genHType degrees);
$pure $genType degrees($genType radians);
$pure $genHType degrees($genHType radians);
$pure $genType sin($genType angle);
$pure $genHType sin($genHType angle);
$pure $genType cos($genType angle);
$pure $genHType cos($genHType angle);
$pure $genType tan($genType angle);
$pure $genHType tan($genHType angle);
$pure $genType asin($genType x);
$pure $genHType asin($genHType x);
$pure $genType acos($genType x);
$pure $genHType acos($genHType x);
$pure $genType atan($genType y, $genType x);
$pure $genHType atan($genHType y, $genHType x);
$pure $genType atan($genType y_over_x);
$pure $genHType atan($genHType y_over_x);
// 8.1 : Angle and Trigonometry Functions (GLSL ES 3.0)
$pure $es3 $genType sinh($genType x);
$pure $es3 $genHType sinh($genHType x);
$pure $es3 $genType cosh($genType x);
$pure $es3 $genHType cosh($genHType x);
$pure $es3 $genType tanh($genType x);
$pure $es3 $genHType tanh($genHType x);
$pure $es3 $genType asinh($genType x);
$pure $es3 $genHType asinh($genHType x);
$pure $es3 $genType acosh($genType x);
$pure $es3 $genHType acosh($genHType x);
$pure $es3 $genType atanh($genType x);
$pure $es3 $genHType atanh($genHType x);
// 8.2 : Exponential Functions
$pure $genType pow($genType x, $genType y);
$pure $genHType pow($genHType x, $genHType y);
$pure $genType exp($genType x);
$pure $genHType exp($genHType x);
$pure $genType log($genType x);
$pure $genHType log($genHType x);
$pure $genType exp2($genType x);
$pure $genHType exp2($genHType x);
$pure $genType log2($genType x);
$pure $genHType log2($genHType x);
$pure $genType sqrt($genType x);
$pure $genHType sqrt($genHType x);
$pure $genType inversesqrt($genType x);
$pure $genHType inversesqrt($genHType x);
// 8.3 : Common Functions
$pure $genType abs($genType x);
$pure $genHType abs($genHType x);
$pure $genType sign($genType x);
$pure $genHType sign($genHType x);
$pure $genType floor($genType x);
$pure $genHType floor($genHType x);
$pure $genType ceil($genType x);
$pure $genHType ceil($genHType x);
$pure $genType fract($genType x);
$pure $genHType fract($genHType x);
$pure $genType mod($genType x, float y);
$pure $genType mod($genType x, $genType y);
$pure $genHType mod($genHType x, half y);
$pure $genHType mod($genHType x, $genHType y);
$pure $genType min($genType x, $genType y);
$pure $genType min($genType x, float y);
$pure $genHType min($genHType x, $genHType y);
$pure $genHType min($genHType x, half y);
$pure $genType max($genType x, $genType y);
$pure $genType max($genType x, float y);
$pure $genHType max($genHType x, $genHType y);
$pure $genHType max($genHType x, half y);
$pure $genType clamp($genType x, $genType minVal, $genType maxVal);
$pure $genType clamp($genType x, float minVal, float maxVal);
$pure $genHType clamp($genHType x, $genHType minVal, $genHType maxVal);
$pure $genHType clamp($genHType x, half minVal, half maxVal);
$pure $genType saturate($genType x); // SkSL extension
$pure $genHType saturate($genHType x); // SkSL extension
$pure $genType mix($genType x, $genType y, $genType a);
$pure $genType mix($genType x, $genType y, float a);
$pure $genHType mix($genHType x, $genHType y, $genHType a);
$pure $genHType mix($genHType x, $genHType y, half a);
$pure $genType step($genType edge, $genType x);
$pure $genType step(float edge, $genType x);
$pure $genHType step($genHType edge, $genHType x);
$pure $genHType step(half edge, $genHType x);
$pure $genType smoothstep($genType edge0, $genType edge1, $genType x);
$pure $genType smoothstep(float edge0, float edge1, $genType x);
$pure $genHType smoothstep($genHType edge0, $genHType edge1, $genHType x);
$pure $genHType smoothstep(half edge0, half edge1, $genHType x);
// 8.3 : Common Functions (GLSL ES 3.0)
$pure $es3 $genIType abs($genIType x);
$pure $es3 $genIType sign($genIType x);
$pure $es3 $genIType floatBitsToInt ($genType value);
$pure $es3 $genUType floatBitsToUint($genType value);
$pure $es3 $genType intBitsToFloat ($genIType value);
$pure $es3 $genType uintBitsToFloat($genUType value);
$pure $es3 $genType trunc($genType x);
$pure $es3 $genHType trunc($genHType x);
$pure $es3 $genType round($genType x);
$pure $es3 $genHType round($genHType x);
$pure $es3 $genType roundEven($genType x);
$pure $es3 $genHType roundEven($genHType x);
$pure $es3 $genIType min($genIType x, $genIType y);
$pure $es3 $genIType min($genIType x, int y);
$pure $es3 $genUType min($genUType x, $genUType y);
$pure $es3 $genUType min($genUType x, uint y);
$pure $es3 $genIType max($genIType x, $genIType y);
$pure $es3 $genIType max($genIType x, int y);
$pure $es3 $genUType max($genUType x, $genUType y);
$pure $es3 $genUType max($genUType x, uint y);
$pure $es3 $genIType clamp($genIType x, $genIType minVal, $genIType maxVal);
$pure $es3 $genIType clamp($genIType x, int minVal, int maxVal);
$pure $es3 $genUType clamp($genUType x, $genUType minVal, $genUType maxVal);
$pure $es3 $genUType clamp($genUType x, uint minVal, uint maxVal);
$pure $es3 $genType mix($genType x, $genType y, $genBType a);
$pure $es3 $genHType mix($genHType x, $genHType y, $genBType a);
// 8.3 : Common Functions (GLSL ES 3.0) -- cannot be used in constant-expressions
$pure $es3 $genBType isnan($genType x);
$pure $es3 $genBType isnan($genHType x);
$pure $es3 $genBType isinf($genType x);
$pure $es3 $genBType isinf($genHType x);
$es3 $genType modf($genType x, out $genType i);
$es3 $genHType modf($genHType x, out $genHType i);
// 8.4 : Floating-Point Pack and Unpack Functions (GLSL ES 3.0)
$pure $es3 uint packUnorm2x16(float2 v);
$pure $es3 float2 unpackUnorm2x16(uint p);
// 8.5 : Geometric Functions
$pure float length($genType x);
$pure half length($genHType x);
$pure float distance($genType p0, $genType p1);
$pure half distance($genHType p0, $genHType p1);
$pure float dot($genType x, $genType y);
$pure half dot($genHType x, $genHType y);
$pure float3 cross(float3 x, float3 y);
$pure half3 cross(half3 x, half3 y);
$pure $genType normalize($genType x);
$pure $genHType normalize($genHType x);
$pure $genType faceforward($genType N, $genType I, $genType Nref);
$pure $genHType faceforward($genHType N, $genHType I, $genHType Nref);
$pure $genType reflect($genType I, $genType N);
$pure $genHType reflect($genHType I, $genHType N);
$pure $genType refract($genType I, $genType N, float eta);
$pure $genHType refract($genHType I, $genHType N, half eta);
// 8.6 : Matrix Functions
$pure $squareMat matrixCompMult($squareMat x, $squareMat y);
$pure $squareHMat matrixCompMult($squareHMat x, $squareHMat y);
$pure $es3 $mat matrixCompMult($mat x, $mat y);
$pure $es3 $hmat matrixCompMult($hmat x, $hmat y);
// 8.6 : Matrix Functions (GLSL 1.4, poly-filled by SkSL as needed)
$pure $squareMat inverse($squareMat m);
$pure $squareHMat inverse($squareHMat m);
// 8.6 : Matrix Functions (GLSL ES 3.0)
$pure $es3 float determinant($squareMat m);
$pure $es3 half determinant($squareHMat m);
$pure $es3 $squareMat transpose($squareMat m);
$pure $es3 $squareHMat transpose($squareHMat m);
$pure $es3 float2x3 transpose(float3x2 m);
$pure $es3 half2x3 transpose(half3x2 m);
$pure $es3 float2x4 transpose(float4x2 m);
$pure $es3 half2x4 transpose(half4x2 m);
$pure $es3 float3x2 transpose(float2x3 m);
$pure $es3 half3x2 transpose(half2x3 m);
$pure $es3 float3x4 transpose(float4x3 m);
$pure $es3 half3x4 transpose(half4x3 m);
$pure $es3 float4x2 transpose(float2x4 m);
$pure $es3 half4x2 transpose(half2x4 m);
$pure $es3 float4x3 transpose(float3x4 m);
$pure $es3 half4x3 transpose(half3x4 m);
$pure $es3 $squareMat outerProduct($vec c, $vec r);
$pure $es3 $squareHMat outerProduct($hvec c, $hvec r);
$pure $es3 float2x3 outerProduct(float3 c, float2 r);
$pure $es3 half2x3 outerProduct(half3 c, half2 r);
$pure $es3 float3x2 outerProduct(float2 c, float3 r);
$pure $es3 half3x2 outerProduct(half2 c, half3 r);
$pure $es3 float2x4 outerProduct(float4 c, float2 r);
$pure $es3 half2x4 outerProduct(half4 c, half2 r);
$pure $es3 float4x2 outerProduct(float2 c, float4 r);
$pure $es3 half4x2 outerProduct(half2 c, half4 r);
$pure $es3 float3x4 outerProduct(float4 c, float3 r);
$pure $es3 half3x4 outerProduct(half4 c, half3 r);
$pure $es3 float4x3 outerProduct(float3 c, float4 r);
$pure $es3 half4x3 outerProduct(half3 c, half4 r);
// 8.7 : Vector Relational Functions
$pure $bvec lessThan($vec x, $vec y);
$pure $bvec lessThan($hvec x, $hvec y);
$pure $bvec lessThan($ivec x, $ivec y);
$pure $bvec lessThan($svec x, $svec y);
$pure $bvec lessThanEqual($vec x, $vec y);
$pure $bvec lessThanEqual($hvec x, $hvec y);
$pure $bvec lessThanEqual($ivec x, $ivec y);
$pure $bvec lessThanEqual($svec x, $svec y);
$pure $bvec greaterThan($vec x, $vec y);
$pure $bvec greaterThan($hvec x, $hvec y);
$pure $bvec greaterThan($ivec x, $ivec y);
$pure $bvec greaterThan($svec x, $svec y);
$pure $bvec greaterThanEqual($vec x, $vec y);
$pure $bvec greaterThanEqual($hvec x, $hvec y);
$pure $bvec greaterThanEqual($ivec x, $ivec y);
$pure $bvec greaterThanEqual($svec x, $svec y);
$pure $bvec equal($vec x, $vec y);
$pure $bvec equal($hvec x, $hvec y);
$pure $bvec equal($ivec x, $ivec y);
$pure $bvec equal($svec x, $svec y);
$pure $bvec equal($bvec x, $bvec y);
$pure $bvec notEqual($vec x, $vec y);
$pure $bvec notEqual($hvec x, $hvec y);
$pure $bvec notEqual($ivec x, $ivec y);
$pure $bvec notEqual($svec x, $svec y);
$pure $bvec notEqual($bvec x, $bvec y);
$pure $es3 $bvec lessThan($usvec x, $usvec y);
$pure $es3 $bvec lessThan($uvec x, $uvec y);
$pure $es3 $bvec lessThanEqual($uvec x, $uvec y);
$pure $es3 $bvec lessThanEqual($usvec x, $usvec y);
$pure $es3 $bvec greaterThan($uvec x, $uvec y);
$pure $es3 $bvec greaterThan($usvec x, $usvec y);
$pure $es3 $bvec greaterThanEqual($uvec x, $uvec y);
$pure $es3 $bvec greaterThanEqual($usvec x, $usvec y);
$pure $es3 $bvec equal($uvec x, $uvec y);
$pure $es3 $bvec equal($usvec x, $usvec y);
$pure $es3 $bvec notEqual($uvec x, $uvec y);
$pure $es3 $bvec notEqual($usvec x, $usvec y);
$pure bool any($bvec x);
$pure bool all($bvec x);
$pure $bvec not($bvec x);
// 8.9 : Fragment Processing Functions (GLSL ES 3.0)
$pure $es3 $genType dFdx($genType p);
$pure $es3 $genType dFdy($genType p);
$pure $es3 $genHType dFdx($genHType p);
$pure $es3 $genHType dFdy($genHType p);
$pure $es3 $genType fwidth($genType p);
$pure $es3 $genHType fwidth($genHType p);
// SkSL utility functions
// The max() guards against division by zero when the incoming color is transparent black
$pure half4 unpremul(half4 color) { return half4 (color.rgb / max(color.a, 0.0001), color.a); }
$pure float4 unpremul(float4 color) { return float4(color.rgb / max(color.a, 0.0001), color.a); }
// Similar, but used for polar-space CSS colors
$export $pure half4 $unpremul_polar(half4 color) {
return half4(color.r, / max(color.a, 0.0001), color.a);
// Convert RGBA -> HSLA (including unpremul).
// Based on work by Sam Hocevar, Emil Persson, and Ian Taylor [1][2][3]. High-level ideas:
// - minimize the number of branches by sorting and computing the hue phase in parallel (vec4s)
// - trade the third sorting branch for a potentially faster std::min and leaving 2nd/3rd
// channels unsorted (based on the observation that swapping both the channels and the bias sign
// has no effect under abs)
// - use epsilon offsets for denominators, to avoid explicit zero-checks
// An additional trick we employ is deferring premul->unpremul conversion until the very end: the
// alpha factor gets naturally simplified for H and S, and only L requires a dedicated unpremul
// division (so we trade three divs for one).
// [1]
// [2]
// [3]
$export $pure half4 $rgb_to_hsl(half3 c, half a) {
half4 p = (c.g < c.b) ? half4(, -1, 2/3.0)
: half4(, 0, -1/3.0);
half4 q = (c.r < p.x) ? half4(p.x, c.r, p.yw)
: half4(c.r, p.x, p.yz);
// q.x -> max channel value
// q.yz -> 2nd/3rd channel values (unsorted)
// q.w -> bias value dependent on max channel selection
const half kEps = 0.0001;
half pmV = q.x;
half pmC = pmV - min(q.y, q.z);
half pmL = pmV - pmC * 0.5;
half H = abs(q.w + (q.y - q.z) / (pmC * 6 + kEps));
half S = pmC / (a + kEps - abs(pmL * 2 - a));
half L = pmL / (a + kEps);
return half4(H, S, L, a);
// Convert HSLA -> RGBA (including clamp and premul).
// Based on work by Sam Hocevar, Emil Persson, and Ian Taylor [1][2][3].
// [1]
// [2]
// [3]
$export $pure half3 $hsl_to_rgb(half3 hsl) {
half C = (1 - abs(2 * hsl.z - 1)) * hsl.y;
half3 p = + half3(0, 2/3.0, 1/3.0);
half3 q = saturate(abs(fract(p) * 6 - 3) - 1);
return (q - 0.5) * C + hsl.z;
$export $pure half4 $hsl_to_rgb(half3 hsl, half a) {
return saturate(half4($hsl_to_rgb(hsl) * a, a));
// Color conversion functions used in gradient interpolation, based on
// TODO(skia:13108): For all of these, we can eliminate any linear math at the beginning
// (by removing the corresponding linear math at the end of the CPU code).
$export $pure half3 $css_lab_to_xyz(half3 lab) {
const half k = 24389 / 27.0;
const half e = 216 / 24389.0;
half3 f;
f[1] = (lab[0] + 16) / 116;
f[0] = (lab[1] / 500) + f[1];
f[2] = f[1] - (lab[2] / 200);
half3 f_cubed = pow(f, half3(3));
half3 xyz = half3(
f_cubed[0] > e ? f_cubed[0] : (116 * f[0] - 16) / k,
lab[0] > k * e ? f_cubed[1] : lab[0] / k,
f_cubed[2] > e ? f_cubed[2] : (116 * f[2] - 16) / k
const half3 D50 = half3(0.3457 / 0.3585, 1.0, (1.0 - 0.3457 - 0.3585) / 0.3585);
return xyz * D50;
// Skia stores all polar colors with hue in the first component, so this "LCH -> Lab" transform
// actually takes "HCL". This is also used to do the same polar transform for OkHCL to OkLAB.
// See similar comments & logic in SkGradientShaderBase.cpp.
$pure half3 $css_hcl_to_lab(half3 hcl) {
return half3(
hcl[1] * cos(radians(hcl[0])),
hcl[1] * sin(radians(hcl[0]))
$export $pure half3 $css_hcl_to_xyz(half3 hcl) {
return $css_lab_to_xyz($css_hcl_to_lab(hcl));
$export $pure half3 $css_oklab_to_linear_srgb(half3 oklab) {
half l_ = oklab.x + 0.3963377774 * oklab.y + 0.2158037573 * oklab.z,
m_ = oklab.x - 0.1055613458 * oklab.y - 0.0638541728 * oklab.z,
s_ = oklab.x - 0.0894841775 * oklab.y - 1.2914855480 * oklab.z;
half l = l_*l_*l_,
m = m_*m_*m_,
s = s_*s_*s_;
return half3(
+4.0767416621 * l - 3.3077115913 * m + 0.2309699292 * s,
-1.2684380046 * l + 2.6097574011 * m - 0.3413193965 * s,
-0.0041960863 * l - 0.7034186147 * m + 1.7076147010 * s
$export $pure half3 $css_okhcl_to_linear_srgb(half3 okhcl) {
return $css_oklab_to_linear_srgb($css_hcl_to_lab(okhcl));
$export $pure half3 $css_oklab_gamut_map_to_linear_srgb(half3 oklab) {
// Constants for the normal vector of the plane formed by white, black, and
// the specified vertex of the gamut.
const half2 normal_R = half2(0.409702, -0.912219);
const half2 normal_M = half2(-0.397919, -0.917421);
const half2 normal_B = half2(-0.906800, 0.421562);
const half2 normal_C = half2(-0.171122, 0.985250);
const half2 normal_G = half2(0.460276, 0.887776);
const half2 normal_Y = half2(0.947925, 0.318495);
// For the triangles formed by white (W) or black (K) with the vertices
// of Yellow and Red (YR), Red and Magenta (RM), etc, the constants to be
// used to compute the intersection of a line of constant hue and luminance
// with that plane.
const half c0_YR = 0.091132;
const half2 cW_YR = half2(0.070370, 0.034139);
const half2 cK_YR = half2(0.018170, 0.378550);
const half c0_RM = 0.113902;
const half2 cW_RM = half2(0.090836, 0.036251);
const half2 cK_RM = half2(0.226781, 0.018764);
const half c0_MB = 0.161739;
const half2 cW_MB = half2(-0.008202, -0.264819);
const half2 cK_MB = half2( 0.187156, -0.284304);
const half c0_BC = 0.102047;
const half2 cW_BC = half2(-0.014804, -0.162608);
const half2 cK_BC = half2(-0.276786, 0.004193);
const half c0_CG = 0.092029;
const half2 cW_CG = half2(-0.038533, -0.001650);
const half2 cK_CG = half2(-0.232572, -0.094331);
const half c0_GY = 0.081709;
const half2 cW_GY = half2(-0.034601, -0.002215);
const half2 cK_GY = half2( 0.012185, 0.338031);
half2 ab = oklab.yz;
// Find the planes to intersect with and set the constants based on those
// planes.
half c0;
half2 cW;
half2 cK;
if (dot(ab, normal_R) < 0.0) {
if (dot(ab, normal_G) < 0.0) {
if (dot(ab, normal_C) < 0.0) {
c0 = c0_BC; cW = cW_BC; cK = cK_BC;
} else {
c0 = c0_CG; cW = cW_CG; cK = cK_CG;
} else {
if (dot(ab, normal_Y) < 0.0) {
c0 = c0_GY; cW = cW_GY; cK = cK_GY;
} else {
c0 = c0_YR; cW = cW_YR; cK = cK_YR;
} else {
if (dot(ab, normal_B) < 0.0) {
if (dot(ab, normal_M) < 0.0) {
c0 = c0_RM; cW = cW_RM; cK = cK_RM;
} else {
c0 = c0_MB; cW = cW_MB; cK = cK_MB;
} else {
c0 = c0_BC; cW = cW_BC; cK = cK_BC;
// Perform the intersection.
half alpha = 1.0;
// Intersect with the plane with white.
half w_denom = dot(cW, ab);
if (w_denom > 0.0) {
half one_minus_L = 1.0 - oklab.r;
half w_num = c0*one_minus_L;
if (w_num < w_denom) {
alpha = min(alpha, w_num / w_denom);
// Intersect with the plane with black.
half k_denom = dot(cK, ab);
if (k_denom > 0.0) {
half L = oklab.r;
half k_num = c0*L;
if (k_num < k_denom) {
alpha = min(alpha, k_num / k_denom);
// Attenuate the ab coordinate by alpha.
oklab.yz *= alpha;
return $css_oklab_to_linear_srgb(oklab);
$export $pure half3 $css_okhcl_gamut_map_to_linear_srgb(half3 okhcl) {
return $css_oklab_gamut_map_to_linear_srgb($css_hcl_to_lab(okhcl));
// TODO(skia:13108): Use our optimized version (though it has different range)
// Doing so might require fixing (re-deriving?) the math for the HWB version below
$export $pure half3 $css_hsl_to_srgb(half3 hsl) {
hsl.x = mod(hsl.x, 360);
if (hsl.x < 0) {
hsl.x += 360;
hsl.yz /= 100;
half3 k = mod(half3(0, 8, 4) + hsl.x/30, 12);
half a = hsl.y * min(hsl.z, 1 - hsl.z);
return hsl.z - a * clamp(min(k - 3, 9 - k), -1, 1);
$export $pure half3 $css_hwb_to_srgb(half3 hwb) {
hwb.yz /= 100;
if (hwb.y + hwb.z >= 1) {
half gray = hwb.y / (hwb.y + hwb.z);
return half3(gray);
half3 rgb = $css_hsl_to_srgb(half3(hwb.x, 100, 50));
rgb *= (1 - hwb.y - hwb.z);
rgb += hwb.y;
return rgb;
* The actual output color space of this function depends on the input color space
* (it might be sRGB, linear sRGB, or linear XYZ). The actual space is what's stored
* in the gradient/SkColor4fXformer's fIntermediateColorSpace.
$export $pure half4 $interpolated_to_rgb_unpremul(half4 color, int colorSpace, int doUnpremul) {
const int kDestination = 0;
const int kSRGBLinear = 1;
const int kLab = 2;
const int kOKLab = 3;
const int kOKLabGamutMap = 4;
const int kLCH = 5;
const int kOKLCH = 6;
const int kOKLCHGamutMap = 7;
const int kSRGB = 8;
const int kHSL = 9;
const int kHWB = 10;
if (bool(doUnpremul)) {
switch (colorSpace) {
case kLab:
case kOKLab:
case kOKLabGamutMap: color = unpremul(color); break;
case kLCH:
case kOKLCH:
case kOKLCHGamutMap:
case kHSL:
case kHWB: color = $unpremul_polar(color); break;
switch (colorSpace) {
case kLab: color.rgb = $css_lab_to_xyz(color.rgb); break;
case kOKLab: color.rgb = $css_oklab_to_linear_srgb(color.rgb); break;
case kOKLabGamutMap: color.rgb = $css_oklab_gamut_map_to_linear_srgb(color.rgb); break;
case kLCH: color.rgb = $css_hcl_to_xyz(color.rgb); break;
case kOKLCH: color.rgb = $css_okhcl_to_linear_srgb(color.rgb); break;
case kOKLCHGamutMap: color.rgb = $css_okhcl_gamut_map_to_linear_srgb(color.rgb); break;
case kHSL: color.rgb = $css_hsl_to_srgb(color.rgb); break;
case kHWB: color.rgb = $css_hwb_to_srgb(color.rgb); break;
return color;