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(Conditionally) add further dithering algorithms

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jpirnay
2026-04-06 17:23:29 +02:00
parent 0ba4626157
commit 4f031b00b1
8 changed files with 102 additions and 6 deletions
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lib/Epub/Epub/converters/JpegToFramebufferConverter.cpp
+29 -2
View File
@@ -1,6 +1,8 @@
#include "JpegToFramebufferConverter.h"
#ifdef ENABLE_IMAGE_DITHERING_EXTENSION
#include <BitmapHelpers.h>
#endif
#include <FsHelpers.h>
#include <GfxRenderer.h>
#include <HalStorage.h>
@@ -40,9 +42,11 @@ struct JpegContext {
PixelCache cache;
bool caching;
#ifdef ENABLE_IMAGE_DITHERING_EXTENSION
int currentDitherRow;
AtkinsonDitherer* atkinsonDitherer;
DiffusedBayerDitherer* diffusedBayerDitherer;
#endif
JpegContext()
: renderer(nullptr),
@@ -55,17 +59,25 @@ struct JpegContext {
dstHeight(0),
fineScaleFP(1 << 16),
invScaleFP(1 << 16),
caching(false),
caching(false)
#ifdef ENABLE_IMAGE_DITHERING_EXTENSION
,
currentDitherRow(-1),
atkinsonDitherer(nullptr),
diffusedBayerDitherer(nullptr) {}
diffusedBayerDitherer(nullptr)
#endif
{
}
#ifdef ENABLE_IMAGE_DITHERING_EXTENSION
~JpegContext() {
delete atkinsonDitherer;
delete diffusedBayerDitherer;
}
#endif
};
#ifdef ENABLE_IMAGE_DITHERING_EXTENSION
void prepareDitherRow(JpegContext& ctx, int dstY) {
if (!ctx.config || !ctx.config->useDithering) return;
@@ -107,6 +119,13 @@ uint8_t ditherGray(JpegContext& ctx, uint8_t gray, int localX, int outX, int out
return applyBayerDither4Level(gray, outX, outY);
}
#else
uint8_t ditherGray(JpegContext& ctx, uint8_t gray, int localX, int outX, int outY) {
(void)ctx;
(void)localX;
return applyBayerDither4Level(gray, outX, outY);
}
#endif
// File I/O callbacks use pFile->fHandle to access the FsFile*,
// avoiding the need for global file state.
@@ -235,7 +254,9 @@ int jpegDrawCallback(JPEGDRAW* pDraw) {
if (fineScaleFP == FP_ONE) {
for (int dstY = dstYStart; dstY < dstYEnd; dstY++) {
const int outY = cfgY + dstY;
#ifdef ENABLE_IMAGE_DITHERING_EXTENSION
prepareDitherRow(*ctx, dstY);
#endif
pw.beginRow(outY);
if (caching) cw.beginRow(outY, ctx->config->y);
const uint8_t* row = &pixels[(dstY - blockY) * stride];
@@ -264,7 +285,9 @@ int jpegDrawCallback(JPEGDRAW* pDraw) {
for (int dstY = dstYStart; dstY < dstYEnd; dstY++) {
const int outY = cfgY + dstY;
#ifdef ENABLE_IMAGE_DITHERING_EXTENSION
prepareDitherRow(*ctx, dstY);
#endif
pw.beginRow(outY);
if (caching) cw.beginRow(outY, ctx->config->y);
const int32_t srcFyFP = dstY * invScaleFP;
@@ -344,7 +367,9 @@ int jpegDrawCallback(JPEGDRAW* pDraw) {
// === Nearest-neighbor (downscale: fineScale < 1.0) ===
for (int dstY = dstYStart; dstY < dstYEnd; dstY++) {
const int outY = cfgY + dstY;
#ifdef ENABLE_IMAGE_DITHERING_EXTENSION
prepareDitherRow(*ctx, dstY);
#endif
pw.beginRow(outY);
if (caching) cw.beginRow(outY, ctx->config->y);
const int32_t srcFyFP = dstY * invScaleFP;
@@ -507,6 +532,7 @@ bool JpegToFramebufferConverter::decodeToFramebuffer(const std::string& imagePat
}
if (config.useDithering) {
#ifdef ENABLE_IMAGE_DITHERING_EXTENSION
switch (config.ditherMode) {
case ImageDitherMode::Atkinson:
ctx.atkinsonDitherer = new (std::nothrow) AtkinsonDitherer(destWidth);
@@ -525,6 +551,7 @@ bool JpegToFramebufferConverter::decodeToFramebuffer(const std::string& imagePat
default:
break;
}
#endif
}
unsigned long decodeStart = millis();