int GDALColorTable::CreateColorRamp(
int nStartIndex, const GDALColorEntry *psStartColor,
int nEndIndex, const GDALColorEntry *psEndColor )
{
/* validate indexes */
if( nStartIndex < 0 || nStartIndex > 255 ||
nEndIndex < 0 || nEndIndex > 255 ||
nStartIndex > nEndIndex )
{
return -1;
}
/* validate color entries */
if( psStartColor == NULL || psEndColor == NULL )
{
return -1;
}
/* calculate number of colors in-between */
const int nColors = nEndIndex - nStartIndex;
/* set starting color */
SetColorEntry( nStartIndex, psStartColor );
if( nColors == 0 )
{
return GetColorEntryCount(); /* it should not proceed */
}
/* set ending color */
SetColorEntry( nEndIndex, psEndColor );
/* calculate the slope of the linear transformation */
const double dfSlope1 = ( psEndColor->c1 - psStartColor->c1 )
/ static_cast<double>( nColors );
const double dfSlope2 = ( psEndColor->c2 - psStartColor->c2 )
/ static_cast<double>( nColors );
const double dfSlope3 = ( psEndColor->c3 - psStartColor->c3 )
/ static_cast<double>( nColors );
const double dfSlope4 = ( psEndColor->c4 - psStartColor->c4 )
/ static_cast<double>( nColors );
/* loop through the new colors */
GDALColorEntry sColor = *psStartColor;
for( int i = 1; i < nColors; i++ )
{
sColor.c1 = static_cast<short>(
i * dfSlope1 + static_cast<double>( psStartColor->c1 ) );
sColor.c2 = static_cast<short>(
i * dfSlope2 + static_cast<double>( psStartColor->c2 ) );
sColor.c3 = static_cast<short>(
i * dfSlope3 + static_cast<double>( psStartColor->c3 ) );
sColor.c4 = static_cast<short>(
i * dfSlope4 + static_cast<double>( psStartColor->c4 ) );
SetColorEntry( nStartIndex + i, &sColor );
}
/* return the total number of colors */
return GetColorEntryCount();
}
static void SetUpPixmap(void) {
int i, r, g, b;
stColorTable = (CTabHandle) NewHandle(sizeof(ColorTable) + (256 * sizeof(ColorSpec)));
(*stColorTable)->ctSeed = GetCTSeed();
(*stColorTable)->ctFlags = 0;
(*stColorTable)->ctSize = 255;
/* 1-bit colors (monochrome) */
SetColorEntry(0, 65535, 65535, 65535); /* white or transparent */
SetColorEntry(1, 0, 0, 0); /* black */
/* additional colors for 2-bit color */
SetColorEntry(2, 65535, 65535, 65535); /* opaque white */
SetColorEntry(3, 32768, 32768, 32768); /* 1/2 gray */
/* additional colors for 4-bit color */
SetColorEntry( 4, 65535, 0, 0); /* red */
SetColorEntry( 5, 0, 65535, 0); /* green */
SetColorEntry( 6, 0, 0, 65535); /* blue */
SetColorEntry( 7, 0, 65535, 65535); /* cyan */
SetColorEntry( 8, 65535, 65535, 0); /* yellow */
SetColorEntry( 9, 65535, 0, 65535); /* magenta */
SetColorEntry(10, 8192, 8192, 8192); /* 1/8 gray */
SetColorEntry(11, 16384, 16384, 16384); /* 2/8 gray */
SetColorEntry(12, 24576, 24576, 24576); /* 3/8 gray */
SetColorEntry(13, 40959, 40959, 40959); /* 5/8 gray */
SetColorEntry(14, 49151, 49151, 49151); /* 6/8 gray */
SetColorEntry(15, 57343, 57343, 57343); /* 7/8 gray */
/* additional colors for 8-bit color */
/* 24 more shades of gray (does not repeat 1/8th increments) */
SetColorEntry(16, 2048, 2048, 2048); /* 1/32 gray */
SetColorEntry(17, 4096, 4096, 4096); /* 2/32 gray */
SetColorEntry(18, 6144, 6144, 6144); /* 3/32 gray */
SetColorEntry(19, 10240, 10240, 10240); /* 5/32 gray */
SetColorEntry(20, 12288, 12288, 12288); /* 6/32 gray */
SetColorEntry(21, 14336, 14336, 14336); /* 7/32 gray */
SetColorEntry(22, 18432, 18432, 18432); /* 9/32 gray */
SetColorEntry(23, 20480, 20480, 20480); /* 10/32 gray */
SetColorEntry(24, 22528, 22528, 22528); /* 11/32 gray */
SetColorEntry(25, 26624, 26624, 26624); /* 13/32 gray */
SetColorEntry(26, 28672, 28672, 28672); /* 14/32 gray */
SetColorEntry(27, 30720, 30720, 30720); /* 15/32 gray */
SetColorEntry(28, 34815, 34815, 34815); /* 17/32 gray */
SetColorEntry(29, 36863, 36863, 36863); /* 18/32 gray */
SetColorEntry(30, 38911, 38911, 38911); /* 19/32 gray */
SetColorEntry(31, 43007, 43007, 43007); /* 21/32 gray */
SetColorEntry(32, 45055, 45055, 45055); /* 22/32 gray */
SetColorEntry(33, 47103, 47103, 47103); /* 23/32 gray */
SetColorEntry(34, 51199, 51199, 51199); /* 25/32 gray */
SetColorEntry(35, 53247, 53247, 53247); /* 26/32 gray */
SetColorEntry(36, 55295, 55295, 55295); /* 27/32 gray */
SetColorEntry(37, 59391, 59391, 59391); /* 29/32 gray */
SetColorEntry(38, 61439, 61439, 61439); /* 30/32 gray */
SetColorEntry(39, 63487, 63487, 63487); /* 31/32 gray */
/* The remainder of color table defines a color cube with six steps
for each primary color. Note that the corners of this cube repeat
previous colors, but simplifies the mapping between RGB colors and
color map indices. This color cube spans indices 40 through 255.
*/
for (r = 0; r < 6; r++) {
for (g = 0; g < 6; g++) {
for (b = 0; b < 6; b++) {
i = 40 + ((36 * r) + (6 * b) + g);
SetColorEntry(i, (r * 65535) / 5, (g * 65535) / 5, (b * 65535) / 5);
}
}
}
stPixMap = NewPixMap();
(*stPixMap)->pixelType = 0; /* chunky */
(*stPixMap)->cmpCount = 1;
(*stPixMap)->pmTable = stColorTable;
}