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refactor: Deduplicated BMP header writing in Xtc (#1439) by znelson

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This commit is contained in:
jpirnay
2026-04-10 11:29:57 +02:00
parent c42452df8e
commit c97f16b576
4 changed files with 22 additions and 96 deletions
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lib/GfxRenderer/BitmapHelpers.cpp
+6 -6
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@@ -107,7 +107,7 @@ uint8_t quantize1bit(int gray, int x, int y) {
return (gray >= adjustedThreshold) ? 1 : 0;
}
void createBmpHeader(BmpHeader* bmpHeader, int width, int height) {
void createBmpHeader(BmpHeader* bmpHeader, int width, int height, BmpRowOrder rowOrder) {
if (!bmpHeader) return;
// Zero out the memory to ensure no garbage data if called on uninitialized stack memory
@@ -125,15 +125,15 @@ void createBmpHeader(BmpHeader* bmpHeader, int width, int height) {
bmpHeader->infoHeader.biSize = sizeof(bmpHeader->infoHeader);
bmpHeader->infoHeader.biWidth = width;
bmpHeader->infoHeader.biHeight = height;
bmpHeader->infoHeader.biHeight = (rowOrder == BmpRowOrder::TopDown) ? -height : height;
bmpHeader->infoHeader.biPlanes = 1;
bmpHeader->infoHeader.biBitCount = 1;
bmpHeader->infoHeader.biCompression = 0;
bmpHeader->infoHeader.biSizeImage = imageSize;
bmpHeader->infoHeader.biXPelsPerMeter = 0;
bmpHeader->infoHeader.biYPelsPerMeter = 0;
bmpHeader->infoHeader.biClrUsed = 0;
bmpHeader->infoHeader.biClrImportant = 0;
bmpHeader->infoHeader.biXPelsPerMeter = 2835; // 72 DPI
bmpHeader->infoHeader.biYPelsPerMeter = 2835; // 72 DPI
bmpHeader->infoHeader.biClrUsed = 2;
bmpHeader->infoHeader.biClrImportant = 2;
// Color 0 (black)
bmpHeader->colors[0].rgbBlue = 0;
lib/GfxRenderer/BitmapHelpers.h
+3 -1
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@@ -11,8 +11,10 @@ uint8_t quantizeSimple(int gray);
uint8_t quantize1bit(int gray, int x, int y);
int adjustPixel(int gray);
enum class BmpRowOrder { BottomUp, TopDown };
// Populates a 1-bit BMP header in the provided memory.
void createBmpHeader(BmpHeader* bmpHeader, int width, int height);
void createBmpHeader(BmpHeader* bmpHeader, int width, int height, BmpRowOrder rowOrder);
// 1-bit Atkinson dithering - better quality than noise dithering for thumbnails
// Error distribution pattern (same as 2-bit but quantizes to 2 levels):
lib/Xtc/Xtc.cpp
+12 -88
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@@ -7,6 +7,7 @@
#include "Xtc.h"
#include <Bitmap.h>
#include <HalStorage.h>
#include <Logging.h>
@@ -175,52 +176,12 @@ bool Xtc::generateCoverBmp() const {
return false;
}
// Write BMP header
// BMP file header (14 bytes)
const uint32_t rowSize = ((pageInfo.width + 31) / 32) * 4; // Row size aligned to 4 bytes
const uint32_t imageSize = rowSize * pageInfo.height;
const uint32_t fileSize = 14 + 40 + 8 + imageSize; // Header + DIB + palette + data
// Write 1-bit BMP header (top-down row order)
BmpHeader bmpHeader;
createBmpHeader(&bmpHeader, pageInfo.width, pageInfo.height, BmpRowOrder::TopDown);
coverBmp.write(reinterpret_cast<const uint8_t*>(&bmpHeader), sizeof(bmpHeader));
// File header
coverBmp.write('B');
coverBmp.write('M');
coverBmp.write(reinterpret_cast<const uint8_t*>(&fileSize), 4);
uint32_t reserved = 0;
coverBmp.write(reinterpret_cast<const uint8_t*>(&reserved), 4);
uint32_t dataOffset = 14 + 40 + 8; // 1-bit palette has 2 colors (8 bytes)
coverBmp.write(reinterpret_cast<const uint8_t*>(&dataOffset), 4);
// DIB header (BITMAPINFOHEADER - 40 bytes)
uint32_t dibHeaderSize = 40;
coverBmp.write(reinterpret_cast<const uint8_t*>(&dibHeaderSize), 4);
int32_t width = pageInfo.width;
coverBmp.write(reinterpret_cast<const uint8_t*>(&width), 4);
int32_t height = -static_cast<int32_t>(pageInfo.height); // Negative for top-down
coverBmp.write(reinterpret_cast<const uint8_t*>(&height), 4);
uint16_t planes = 1;
coverBmp.write(reinterpret_cast<const uint8_t*>(&planes), 2);
uint16_t bitsPerPixel = 1; // 1-bit monochrome
coverBmp.write(reinterpret_cast<const uint8_t*>(&bitsPerPixel), 2);
uint32_t compression = 0; // BI_RGB (no compression)
coverBmp.write(reinterpret_cast<const uint8_t*>(&compression), 4);
coverBmp.write(reinterpret_cast<const uint8_t*>(&imageSize), 4);
int32_t ppmX = 2835; // 72 DPI
coverBmp.write(reinterpret_cast<const uint8_t*>(&ppmX), 4);
int32_t ppmY = 2835;
coverBmp.write(reinterpret_cast<const uint8_t*>(&ppmY), 4);
uint32_t colorsUsed = 2;
coverBmp.write(reinterpret_cast<const uint8_t*>(&colorsUsed), 4);
uint32_t colorsImportant = 2;
coverBmp.write(reinterpret_cast<const uint8_t*>(&colorsImportant), 4);
// Color palette (2 colors for 1-bit)
// XTC 1-bit polarity: 0 = black, 1 = white (standard BMP palette order)
// Color 0: Black (text/foreground in XTC)
uint8_t black[4] = {0x00, 0x00, 0x00, 0x00};
coverBmp.write(black, 4);
// Color 1: White (background in XTC)
uint8_t white[4] = {0xFF, 0xFF, 0xFF, 0x00};
coverBmp.write(white, 4);
const uint32_t rowSize = ((pageInfo.width + 31) / 32) * 4;
// Write bitmap data
// BMP requires 4-byte row alignment
@@ -403,49 +364,12 @@ bool Xtc::generateThumbBmp(int height) const {
return false;
}
// Write 1-bit BMP header for fast home screen rendering
const uint32_t rowSize = (thumbWidth + 31) / 32 * 4; // 1 bit per pixel, aligned to 4 bytes
const uint32_t imageSize = rowSize * thumbHeight;
const uint32_t fileSize = 14 + 40 + 8 + imageSize; // 8 bytes for 2-color palette
// Write 1-bit BMP header (top-down row order)
BmpHeader bmpHeader;
createBmpHeader(&bmpHeader, thumbWidth, thumbHeight, BmpRowOrder::TopDown);
thumbBmp.write(reinterpret_cast<const uint8_t*>(&bmpHeader), sizeof(bmpHeader));
// File header
thumbBmp.write('B');
thumbBmp.write('M');
thumbBmp.write(reinterpret_cast<const uint8_t*>(&fileSize), 4);
uint32_t reserved = 0;
thumbBmp.write(reinterpret_cast<const uint8_t*>(&reserved), 4);
uint32_t dataOffset = 14 + 40 + 8; // 1-bit palette has 2 colors (8 bytes)
thumbBmp.write(reinterpret_cast<const uint8_t*>(&dataOffset), 4);
// DIB header
uint32_t dibHeaderSize = 40;
thumbBmp.write(reinterpret_cast<const uint8_t*>(&dibHeaderSize), 4);
int32_t widthVal = thumbWidth;
thumbBmp.write(reinterpret_cast<const uint8_t*>(&widthVal), 4);
int32_t heightVal = -static_cast<int32_t>(thumbHeight); // Negative for top-down
thumbBmp.write(reinterpret_cast<const uint8_t*>(&heightVal), 4);
uint16_t planes = 1;
thumbBmp.write(reinterpret_cast<const uint8_t*>(&planes), 2);
uint16_t bitsPerPixel = 1; // 1-bit for black and white
thumbBmp.write(reinterpret_cast<const uint8_t*>(&bitsPerPixel), 2);
uint32_t compression = 0;
thumbBmp.write(reinterpret_cast<const uint8_t*>(&compression), 4);
thumbBmp.write(reinterpret_cast<const uint8_t*>(&imageSize), 4);
int32_t ppmX = 2835;
thumbBmp.write(reinterpret_cast<const uint8_t*>(&ppmX), 4);
int32_t ppmY = 2835;
thumbBmp.write(reinterpret_cast<const uint8_t*>(&ppmY), 4);
uint32_t colorsUsed = 2;
thumbBmp.write(reinterpret_cast<const uint8_t*>(&colorsUsed), 4);
uint32_t colorsImportant = 2;
thumbBmp.write(reinterpret_cast<const uint8_t*>(&colorsImportant), 4);
// Color palette (2 colors for 1-bit: black and white)
uint8_t palette[8] = {
0x00, 0x00, 0x00, 0x00, // Color 0: Black
0xFF, 0xFF, 0xFF, 0x00 // Color 1: White
};
thumbBmp.write(palette, 8);
const uint32_t rowSize = (thumbWidth + 31) / 32 * 4;
// Allocate row buffer for 1-bit output
uint8_t* rowBuffer = static_cast<uint8_t*>(malloc(rowSize));
@@ -628,4 +552,4 @@ void Xtc::prefetchPages(uint32_t pageIndex) const {
return;
}
parser->prefetchWindow(pageIndex);
}
}
src/util/ScreenshotUtil.cpp
+1 -1
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@@ -62,7 +62,7 @@ bool ScreenshotUtil::saveFramebufferAsBmp(const char* filename, const uint8_t* f
BmpHeader header;
createBmpHeader(&header, phyWidth, phyHeight);
createBmpHeader(&header, phyWidth, phyHeight, BmpRowOrder::BottomUp);
bool write_error = false;
if (file.write(reinterpret_cast<uint8_t*>(&header), sizeof(header)) != sizeof(header)) {