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Default covers + optimisations

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This commit is contained in:
jpirnay
2026-05-19 12:34:54 +02:00
parent d2f660ea64
commit 5fec0e0210
10 changed files with 177 additions and 8 deletions
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lib/JpegToBmpConverter/JpegToBmpConverter.cpp
+37 -5
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@@ -457,9 +457,41 @@ bool JpegToBmpConverter::jpegFileToBmpStreamInternal(FsFile& jpegFile, Print& bm
return false;
}
const int effectiveSrcW = progressive ? (srcWidth + 7) / 8 : srcWidth;
const int effectiveSrcH = progressive ? (srcHeight + 7) / 8 : srcHeight;
const int decodeFlags = progressive ? JPEG_SCALE_EIGHTH : 0;
// Progressive JPEGs must stay at 1/8 (DC-only mode, only safe scale with MCU_SKIP patch).
// For baseline JPEGs with a target size, pick the largest built-in DCT scale that still
// keeps the decoded image >= the target — the custom scaler handles the fine remainder.
// This avoids decoding millions of pixels that are immediately thrown away.
int jpegDecodeFlags = 0;
int jpegScaleDenom = 1;
if (progressive) {
jpegDecodeFlags = JPEG_SCALE_EIGHTH;
jpegScaleDenom = 8;
} else if (targetWidth > 0 && targetHeight > 0) {
// Use max(scaleX, scaleY) as the constraint: the DCT pre-scale must keep BOTH axes
// >= target so the fine scaler always downscales (never upscales) on either axis.
// This is safe for both crop=true (which uses max scale) and crop=false (uses min scale).
const float scaleX = static_cast<float>(targetWidth) / srcWidth;
const float scaleY = static_cast<float>(targetHeight) / srcHeight;
const float scaleMax = scaleX > scaleY ? scaleX : scaleY;
if (scaleMax <= 0.125f) {
jpegDecodeFlags = JPEG_SCALE_EIGHTH;
jpegScaleDenom = 8;
} else if (scaleMax <= 0.25f) {
jpegDecodeFlags = JPEG_SCALE_QUARTER;
jpegScaleDenom = 4;
} else if (scaleMax <= 0.5f) {
jpegDecodeFlags = JPEG_SCALE_HALF;
jpegScaleDenom = 2;
}
}
const int effectiveSrcW = (srcWidth + jpegScaleDenom - 1) / jpegScaleDenom;
const int effectiveSrcH = (srcHeight + jpegScaleDenom - 1) / jpegScaleDenom;
if (jpegScaleDenom > 1) {
LOG_DBG("JPG", "Using JPEGDEC 1/%d DCT scale: %dx%d -> %dx%d", jpegScaleDenom, srcWidth, srcHeight, effectiveSrcW,
effectiveSrcH);
}
// Calculate output dimensions (pre-scale to fit display exactly)
int outWidth = effectiveSrcW;
@@ -487,7 +519,7 @@ bool JpegToBmpConverter::jpegFileToBmpStreamInternal(FsFile& jpegFile, Print& bm
scaleY_fp = (static_cast<uint32_t>(effectiveSrcH) << 16) / outHeight;
needsScaling = true;
LOG_DBG("JPG", "Scaling %dx%d -> %dx%d (target %dx%d)", effectiveSrcW, effectiveSrcH, outWidth, outHeight,
LOG_DBG("JPG", "Fine-scaling %dx%d -> %dx%d (target %dx%d)", effectiveSrcW, effectiveSrcH, outWidth, outHeight,
targetWidth, targetHeight);
}
@@ -570,7 +602,7 @@ bool JpegToBmpConverter::jpegFileToBmpStreamInternal(FsFile& jpegFile, Print& bm
jpeg->setPixelType(EIGHT_BIT_GRAYSCALE);
jpeg->setUserPointer(&ctx);
rc = jpeg->decode(0, 0, decodeFlags);
rc = jpeg->decode(0, 0, jpegDecodeFlags);
if (rc != 1 || ctx.error) {
LOG_ERR("JPG", "JPEG decode failed (rc=%d, err=%d)", rc, jpeg->getLastError());