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Implement more precise palette conversion in Palette::save. This makes the output look more like the original (compared against E-UAE), but still not perfect.

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svn-id: r44221
This commit is contained in:
Johannes Schickel 2009-09-20 22:59:30 +00:00
parent a9f1063ae1
commit 6b9299e863
1 changed files with 26 additions and 19 deletions
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45
engines/cine/pal.cpp
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@ -103,14 +103,7 @@ void loadRelatedPalette(const char *fileName) {
}
}
/*! \brief Shift byte to the left by given amount (Handles negative shifting amounts too, otherwise this would be trivial). */
byte shiftByteLeft(const byte value, const signed shiftLeft) {
if (shiftLeft >= 0)
return value << shiftLeft;
else // right shift with negative shiftLeft values
return value >> abs(shiftLeft);
}
namespace {
/*! \brief Is given endian type big endian? (Handles native endian type too, otherwise this would be trivial). */
bool isBigEndian(const EndianType endian) {
assert(endian == CINE_NATIVE_ENDIAN || endian == CINE_LITTLE_ENDIAN || endian == CINE_BIG_ENDIAN);
@ -138,6 +131,15 @@ int bytePos(const int bitPos, const int numBytes, const bool bigEndian) {
return bitPos / 8;
}
/*! \brief Calculate the value of "base" to the power of "power". */
int power(int base, int power) {
int result = 1;
while (power--)
result *= base;
return result;
}
} // end of anonymous namespace
// a.k.a. palRotate
Palette &Palette::rotateRight(byte firstIndex, byte lastIndex, signed rotationAmount) {
assert(rotationAmount == 0 || rotationAmount == 1);
@ -317,25 +319,30 @@ byte *Palette::save(byte *buf, const uint size, const Graphics::PixelFormat form
// Clear the part of the output palette we're going to be writing to with all black
memset(buf, 0, format.bytesPerPixel * numColors);
// Calculate how much bit shifting the color components need (for positioning them correctly)
const signed rShiftLeft = (colorFormat().rLoss - (signed) format.rLoss) + (format.rShift % 8);
const signed gShiftLeft = (colorFormat().gLoss - (signed) format.gLoss) + (format.gShift % 8);
const signed bShiftLeft = (colorFormat().bLoss - (signed) format.bLoss) + (format.bShift % 8);
// Calculate original R/G/B max values
const int rOrigMax = power(2, 8 - colorFormat().rLoss) - 1;
const int gOrigMax = power(2, 8 - colorFormat().gLoss) - 1;
const int bOrigMax = power(2, 8 - colorFormat().bLoss) - 1;
// Calculate the byte masks for each color component (for masking away excess bits)
const byte rMask = format.rMax() << (format.rShift % 8);
const byte gMask = format.gMax() << (format.gShift % 8);
const byte bMask = format.bMax() << (format.bShift % 8);
// Calculate new R/G/B max values
const int rNewMax = power(2, 8 - format.rLoss) - 1;
const int gNewMax = power(2, 8 - format.gLoss) - 1;
const int bNewMax = power(2, 8 - format.bLoss) - 1;
// Calculate the byte position
const int rBytePos = bytePos(format.rShift, format.bytesPerPixel, isBigEndian(endian));
const int gBytePos = bytePos(format.gShift, format.bytesPerPixel, isBigEndian(endian));
const int bBytePos = bytePos(format.bShift, format.bytesPerPixel, isBigEndian(endian));
// Save the palette to the output in the specified format
for (uint i = firstIndex; i < firstIndex + numColors; i++) {
buf[i * format.bytesPerPixel + rBytePos] |= (shiftByteLeft(_colors[i].r, rShiftLeft) & rMask);
buf[i * format.bytesPerPixel + gBytePos] |= (shiftByteLeft(_colors[i].g, gShiftLeft) & gMask);
buf[i * format.bytesPerPixel + bBytePos] |= (shiftByteLeft(_colors[i].b, bShiftLeft) & bMask);
const uint r = (_colors[i].r * rNewMax) / rOrigMax;
const uint g = (_colors[i].g * gNewMax) / gOrigMax;
const uint b = (_colors[i].b * bNewMax) / bOrigMax;
buf[i * format.bytesPerPixel + rBytePos] |= r << (format.rShift % 8);
buf[i * format.bytesPerPixel + gBytePos] |= g << (format.gShift % 8);
buf[i * format.bytesPerPixel + bBytePos] |= b << (format.bShift % 8);
}
// Return the pointer to the output palette