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RGBE conversion fixes.

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This commit is contained in:
castano 2011-09-28 19:53:02 +00:00
parent e15aa7a9bf
commit d87b7edd5f
1 changed files with 40 additions and 22 deletions
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62
src/nvtt/Surface.cpp
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@ -1466,21 +1466,30 @@ void Surface::toRGBE(int mantissaBits, int exponentBits)
float M = max(R, G, B);
// Preliminary exponent:
float E = max(- exponentBias - 1, ifloor(log2f(M))) + 1 + exponentBias;
int E = max(- exponentBias - 1, floatExponent(M)) + 1 + exponentBias;
nvDebugCheck(E >= 0 && E < (1 << exponentBits));
double denom = pow(2, E - exponentBias - mantissaBits);
// Refine exponent:
int max_s = iround(M / exp2(E - exponentBias - mantissaBits));
if (max_s == (1 << mantissaBits)) E += 1.0f;
int m = iround(M / denom);
nvDebugCheck(m <= (1 << mantissaBits));
R = floatRound(R / exp2(E - exponentBias - mantissaBits));
G = floatRound(G / exp2(E - exponentBias - mantissaBits));
B = floatRound(B / exp2(E - exponentBias - mantissaBits));
if (m == (1 << mantissaBits)) {
denom *= 2;
E += 1;
nvDebugCheck(E < (1 << exponentBits));
}
nvDebugCheck(R >= 0 && R <= ((1 << mantissaBits) - 1));
nvDebugCheck(G >= 0 && G <= ((1 << mantissaBits) - 1));
nvDebugCheck(B >= 0 && B <= ((1 << mantissaBits) - 1));
R = floatRound(R / denom);
G = floatRound(G / denom);
B = floatRound(B / denom);
// Store in [0, 1] range.
nvDebugCheck(R >= 0 && R < (1 << mantissaBits));
nvDebugCheck(G >= 0 && G < (1 << mantissaBits));
nvDebugCheck(B >= 0 && B < (1 << mantissaBits));
// Store as normalized float.
r[i] = R / ((1 << mantissaBits) - 1);
g[i] = G / ((1 << mantissaBits) - 1);
b[i] = B / ((1 << mantissaBits) - 1);
@ -1499,13 +1508,22 @@ void Surface::fromRGBE(int mantissaBits, int exponentBits)
// RGB components (ignoring the "Conversion to floating-point" section
// below in this case) as follows:
//
// red = p_red * 2^(p_exp - B - N)
// green = p_green * 2^(p_exp - B - N)
// blue = p_blue * 2^(p_exp - B - N)
// red = p_red * 2^(p_exp - B - N)
// green = p_green * 2^(p_exp - B - N)
// blue = p_blue * 2^(p_exp - B - N)
//
// where B is 15 (the exponent bias) and N is 9 (the number of mantissa
// bits)."
// int exponent = v.field.biasedexponent - RGB9E5_EXP_BIAS - RGB9E5_MANTISSA_BITS;
// float scale = (float) pow(2, exponent);
//
// retval[0] = v.field.r * scale;
// retval[1] = v.field.g * scale;
// retval[2] = v.field.b * scale;
if (isNull()) return;
detach();
@ -1521,17 +1539,17 @@ void Surface::fromRGBE(int mantissaBits, int exponentBits)
const uint count = img->pixelCount();
for (uint i = 0; i < count; i++) {
// RGBE are assumed to be in the [0, 1] range.
float R = r[i] * ((1 << mantissaBits) - 1);
float G = g[i] * ((1 << mantissaBits) - 1);
float B = b[i] * ((1 << mantissaBits) - 1);
float E = a[i] * ((1 << exponentBits) - 1);
// Expand normalized float to to 9995
int R = iround(r[i] * ((1 << mantissaBits) - 1));
int G = iround(g[i] * ((1 << mantissaBits) - 1));
int B = iround(b[i] * ((1 << mantissaBits) - 1));
int E = iround(a[i] * ((1 << exponentBits) - 1));
float M = pow(2, E - exponentBias - mantissaBits);
float scale = powf(2, E - exponentBias - mantissaBits);
r[i] = R * M;
g[i] = G * M;
b[i] = B * M;
r[i] = R * scale;
g[i] = G * scale;
b[i] = B * scale;
a[i] = 1;
}
}