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I should probably have tried to build that first xD

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This commit is contained in:
NiLuJe 2019-05-24 02:05:19 +02:00
parent 81b303aa18
commit 4f754d518a
1 changed files with 10 additions and 3 deletions
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13
src/calibre/utils/imageops/ordered_dither.cpp
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@ -25,6 +25,13 @@ typedef unsigned __int32 uint32_t;
#include <cstdint> #include <cstdint>
#endif #endif
// NOTE: *May* not behave any better than a simple / 0xFF on modern x86_64 CPUs...
// This was, however, tested on ARM, where it is noticeably faster.
static uint32_t DIV255(uint32_t v) {
v += 128;
return (((v >> 8U) + v) >> 8U);
}
// Quantize an 8-bit color value down to a palette of 16 evenly spaced colors, using an ordered 8x8 dithering pattern. // Quantize an 8-bit color value down to a palette of 16 evenly spaced colors, using an ordered 8x8 dithering pattern.
// With a grayscale input, this happens to match the eInk palette perfectly ;). // With a grayscale input, this happens to match the eInk palette perfectly ;).
// If the input is not grayscale, and the output fb is not grayscale either, // If the input is not grayscale, and the output fb is not grayscale either,
@ -64,7 +71,7 @@ static uint8_t
// NOTE: We're doing unsigned maths, so, clamping is basically MIN(q, UINT8_MAX) ;). // NOTE: We're doing unsigned maths, so, clamping is basically MIN(q, UINT8_MAX) ;).
// The only overflow we should ever catch should be for a few black (v = 0xFF) input pixels // The only overflow we should ever catch should be for a few black (v = 0xFF) input pixels
// that get shifted to the next step (i.e., q = 272 (0xFF + 17)). // that get shifted to the next step (i.e., q = 272 (0xFF + 17)).
return (q > UINT8_MAX ? UINT8_MAX : reinterpret_cast<uint8_t>(q); return (q > UINT8_MAX ? UINT8_MAX : static_cast<uint8_t>(q));
} }
QImage ordered_dither(const QImage &image) { // {{{ QImage ordered_dither(const QImage &image) { // {{{
@ -82,11 +89,11 @@ QImage ordered_dither(const QImage &image) { // {{{
for (y = 0; y < height; y++) { for (y = 0; y < height; y++) {
const QRgb *src_row = reinterpret_cast<const QRgb*>(img.constScanLine(y)); const QRgb *src_row = reinterpret_cast<const QRgb*>(img.constScanLine(y));
uint8_t *dst_row = dst.scanLine(r); uint8_t *dst_row = dst.scanLine(y);
for (x = 0; x < width; x++) { for (x = 0; x < width; x++) {
const QRgb pixel = *(src_row + x); const QRgb pixel = *(src_row + x);
// We're running behind grayscale_image, so R = G = B // We're running behind grayscale_image, so R = G = B
gray = qRed(*pixel); gray = qRed(pixel);
dithered = dither_o8x8(x, y, gray); dithered = dither_o8x8(x, y, gray);
*(dst_row + x) = dithered; *(dst_row + x) = dithered;
} }