Optimisation of Bitmap parsing
This commit is contained in:
Dave Allie
parent
f72d2c372c
commit
06bb39e03a
@ -99,18 +99,15 @@ BmpReaderError Bitmap::parseHeaders() {
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if (width <= 0 || height <= 0) return BmpReaderError::BadDimensions;
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// Palette for 8-bit indexed images
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for (int i = 0; i < 256; i++) paletteLum[i] = static_cast<uint8_t>(i); // default grayscale ramp
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// Pre-calculate Row Bytes to avoid doing this every row
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rowBytes = (width * bpp + 31) / 32 * 4;
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for (int i = 0; i < 256; i++) paletteLum[i] = static_cast<uint8_t>(i);
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if (colorsUsed > 0) {
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for (uint32_t i = 0; i < colorsUsed; i++) {
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const int b = file.read();
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const int g = file.read();
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const int r = file.read();
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file.seek(1, SeekCur); // reserved
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const auto bb = static_cast<uint8_t>(b < 0 ? 0 : b);
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const auto gg = static_cast<uint8_t>(g < 0 ? 0 : g);
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const auto rr = static_cast<uint8_t>(r < 0 ? 0 : r);
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paletteLum[i] = static_cast<uint8_t>((77u * rr + 150u * gg + 29u * bb) >> 8);
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uint8_t rgb[4];
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file.read(rgb, 4); // Read B, G, R, Reserved in one go
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paletteLum[i] = (77u * rgb[2] + 150u * rgb[1] + 29u * rgb[0]) >> 8;
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}
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}
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@ -122,72 +119,64 @@ BmpReaderError Bitmap::parseHeaders() {
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}
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// packed 2bpp output, 0 = black, 1 = dark gray, 2 = light gray, 3 = white
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BmpReaderError Bitmap::readRow(uint8_t* data, const size_t dataLen, size_t* read) const {
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// Validate data is long enough to hold a row worth of data
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const size_t outputBytes = (width + 3) / 4;
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if (dataLen < outputBytes) {
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*read = 0;
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return BmpReaderError::BufferTooSmall;
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}
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BmpReaderError Bitmap::readRow(uint8_t* data, uint8_t* rowBuffer) const {
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// Note: rowBuffer should be pre-allocated by the caller to size 'rowBytes'
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if (file.read(rowBuffer, rowBytes) != rowBytes) return BmpReaderError::ShortReadRow;
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// setup data to be all black
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memset(data, 0x00, outputBytes);
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uint8_t* outPtr = data;
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uint8_t currentOutByte = 0;
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int bitShift = 6;
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const size_t rowBytes = (width * bpp + 31) / 32 * 4;
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const auto rowBuffer = static_cast<uint8_t*>(malloc(rowBytes));
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if (!rowBuffer) {
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*read = 0;
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return BmpReaderError::OomRowBuffer;
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}
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if (file.read(rowBuffer, rowBytes) != rowBytes) {
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free(rowBuffer);
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*read = 0;
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return BmpReaderError::ShortReadRow;
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}
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for (int bmpX = 0; bmpX < width; bmpX++) {
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uint8_t lum;
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if (bpp == 1) {
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const uint8_t byte = rowBuffer[bmpX / 8];
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const uint8_t bit = 7 - (bmpX % 8);
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const bool bitSet = (byte >> bit) & 0x01;
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// In 1bpp BMPs, palette index 0 is conventionally black and index 1 is white.
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lum = bitSet ? 0xFF : 0x00;
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} else if (bpp == 2) {
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const uint8_t byte = rowBuffer[bmpX / 4];
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const uint8_t twobit = 6 - ((bmpX * 2) % 8);
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const uint8_t val = (byte >> twobit) & 0x3;
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lum = paletteLum[val];
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} else if (bpp == 8) {
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const uint8_t idx = rowBuffer[bmpX];
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lum = paletteLum[idx];
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// Helper lambda to pack 2bpp color into the output stream
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auto packPixel = [&](uint8_t lum) {
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uint8_t color = (lum >> 6); // Simple 2-bit reduction: 0-255 -> 0-3
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currentOutByte |= (color << bitShift);
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if (bitShift == 0) {
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*outPtr++ = currentOutByte;
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currentOutByte = 0;
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bitShift = 6;
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} else {
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// 24 / 32
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const uint8_t* px = &rowBuffer[bmpX * bpp / 8];
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const uint8_t b = px[0];
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const uint8_t g = px[1];
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const uint8_t r = px[2];
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bitShift -= 2;
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}
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};
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lum = static_cast<uint8_t>((77u * r + 150u * g + 29u * b) >> 8);
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switch (bpp) {
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case 8: {
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for (int x = 0; x < width; x++) {
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packPixel(paletteLum[rowBuffer[x]]);
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}
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break;
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}
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case 24: {
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const uint8_t* p = rowBuffer;
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for (int x = 0; x < width; x++) {
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uint8_t lum = (77u * p[2] + 150u * p[1] + 29u * p[0]) >> 8;
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packPixel(lum);
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p += 3;
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}
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break;
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}
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case 1: {
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for (int x = 0; x < width; x++) {
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uint8_t lum = (rowBuffer[x >> 3] & (0x80 >> (x & 7))) ? 0xFF : 0x00;
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packPixel(lum);
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}
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break;
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}
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case 32: {
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const uint8_t* p = rowBuffer;
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for (int x = 0; x < width; x++) {
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uint8_t lum = (77u * p[2] + 150u * p[1] + 29u * p[0]) >> 8;
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packPixel(lum);
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p += 4;
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}
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break;
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}
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}
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uint8_t color;
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if (lum >= 192) {
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color = 0x3; // white
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} else if (lum >= 128) {
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color = 0x2; // light gray
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} else if (lum >= 64) {
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color = 0x1; // dark gray
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} else {
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color = 0x0; // black
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}
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// Flush remaining bits if width is not a multiple of 4
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if (bitShift != 6) *outPtr = currentOutByte;
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data[bmpX / 4] |= (color << (6 - ((bmpX % 4) * 2)));
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}
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free(rowBuffer);
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*read = outputBytes;
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return BmpReaderError::Ok;
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}
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@ -27,14 +27,15 @@ class Bitmap {
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public:
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static const char* errorToString(BmpReaderError err);
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explicit Bitmap(File& file) : file(file) {};
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explicit Bitmap(File& file) : file(file) {}
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BmpReaderError parseHeaders();
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BmpReaderError readRow(uint8_t* data, size_t dataLen, size_t* read) const;
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BmpReaderError readRow(uint8_t* data, uint8_t* rowBuffer) const;
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BmpReaderError rewindToData() const;
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int getWidth() const { return width; }
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int getHeight() const { return height; }
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bool isTopDown() const { return topDown; }
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bool hasGreyscale() const { return bpp > 1; }
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int getRowBytes() const { return rowBytes; }
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private:
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static uint16_t readLE16(File& f);
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@ -46,5 +47,6 @@ class Bitmap {
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bool topDown = false;
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uint32_t bfOffBits = 0;
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uint16_t bpp = 0;
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int rowBytes = 0;
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uint8_t paletteLum[256] = {};
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};
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@ -134,6 +134,7 @@ void GfxRenderer::drawBitmap(const Bitmap& bitmap, const int x, const int y, con
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const uint8_t outputRowSize = (bitmap.getWidth() + 3) / 4;
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auto* outputRow = static_cast<uint8_t*>(malloc(outputRowSize));
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auto* rowBytes = static_cast<uint8_t*>(malloc(bitmap.getRowBytes()));
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for (int bmpY = 0; bmpY < bitmap.getHeight(); bmpY++) {
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// The BMP's (0, 0) is the bottom-left corner (if the height is positive, top-left if negative).
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@ -146,18 +147,13 @@ void GfxRenderer::drawBitmap(const Bitmap& bitmap, const int x, const int y, con
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break;
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}
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size_t readBytes;
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if (bitmap.readRow(outputRow, outputRowSize, &readBytes) != BmpReaderError::Ok) {
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if (bitmap.readRow(outputRow, rowBytes) != BmpReaderError::Ok) {
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Serial.printf("[%lu] [GFX] Failed to read row %d from bitmap\n", millis(), bmpY);
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free(outputRow);
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free(rowBytes);
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return;
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}
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if (readBytes != outputRowSize) {
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Serial.printf("[%lu] [GFX] Failed to read BMP row data, got: %d, expected: %d\n", millis(), readBytes,
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outputRowSize);
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break;
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}
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for (int bmpX = 0; bmpX < bitmap.getWidth(); bmpX++) {
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int screenX = x + bmpX;
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if (isScaled) {
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@ -180,6 +176,7 @@ void GfxRenderer::drawBitmap(const Bitmap& bitmap, const int x, const int y, con
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}
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free(outputRow);
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free(rowBytes);
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}
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void GfxRenderer::clearScreen(const uint8_t color) const { einkDisplay.clearScreen(color); }
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