static void
convertRaster(FILE * const ifP,
unsigned int const cols,
unsigned int const rows,
pixval const maxval,
int const format,
pixel * const inputRow,
gray * const outputRow,
FILE * const ofP) {
unsigned int row;
for (row = 0; row < rows; ++row) {
ppm_readppmrow( ifP, inputRow, cols, maxval, format );
if (maxval <= 255) {
/* Use fast approximation to 0.299 r + 0.587 g + 0.114 b */
unsigned int col;
for (col = 0; col < cols; ++col)
outputRow[col] = (gray) ppm_fastlumin(inputRow[col]);
} else {
/* Can't use fast approximation, so fall back on floats. */
unsigned int col;
for (col = 0; col < cols; ++col)
outputRow[col] = ppm_luminosity(inputRow[col]);
}
pgm_writepgmrow(ofP, outputRow, cols, maxval, 0);
}
}
static void
computeGrayscaleRow(const pixel * const inputRow,
gray * const outputRow,
pixval const maxval,
unsigned int const cols) {
if (maxval <= 255) {
unsigned int col;
/* Use fast approximation to 0.299 r + 0.587 g + 0.114 b. */
for (col = 0; col < cols; ++col)
outputRow[col] = ppm_fastlumin(inputRow[col]);
} else {
unsigned int col;
/* Can't use fast approximation, so fall back on floats. */
for (col = 0; col < cols; ++col)
outputRow[col] = PPM_LUMIN(inputRow[col]) + 0.5;
}
}
