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fix: Implement guide-based cover image fallback (#830)

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This partially fixes #769 but is dependent upon PR #827 being merged
along side this @daveallie. I removed my PNG conversion code after
finding out that PR was already created. Without this PR though that
book in #769 will still fail to load because of how it's stored in the
file

---------

Co-authored-by: Dave Allie <dave@daveallie.com>
This commit is contained in:
Justin Mitchell
2026-02-16 07:24:30 -05:00
committed by GitHub
parent 0bc6747483
commit 6702060960
3 changed files with 59 additions and 11 deletions
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48
lib/Epub/Epub.cpp
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@@ -77,6 +77,54 @@ bool Epub::parseContentOpf(BookMetadataCache::BookMetadata& bookMetadata) {
bookMetadata.author = opfParser.author;
bookMetadata.language = opfParser.language;
bookMetadata.coverItemHref = opfParser.coverItemHref;
// Guide-based cover fallback: if no cover found via metadata/properties,
// try extracting the image reference from the guide's cover page XHTML
if (bookMetadata.coverItemHref.empty() && !opfParser.guideCoverPageHref.empty()) {
LOG_DBG("EBP", "No cover from metadata, trying guide cover page: %s", opfParser.guideCoverPageHref.c_str());
size_t coverPageSize;
uint8_t* coverPageData = readItemContentsToBytes(opfParser.guideCoverPageHref, &coverPageSize, true);
if (coverPageData) {
const std::string coverPageHtml(reinterpret_cast<char*>(coverPageData), coverPageSize);
free(coverPageData);
// Determine base path of the cover page for resolving relative image references
std::string coverPageBase;
const auto lastSlash = opfParser.guideCoverPageHref.rfind('/');
if (lastSlash != std::string::npos) {
coverPageBase = opfParser.guideCoverPageHref.substr(0, lastSlash + 1);
}
// Search for image references: xlink:href="..." (SVG) and src="..." (img)
std::string imageRef;
for (const char* pattern : {"xlink:href=\"", "src=\""}) {
auto pos = coverPageHtml.find(pattern);
while (pos != std::string::npos) {
pos += strlen(pattern);
const auto endPos = coverPageHtml.find('"', pos);
if (endPos != std::string::npos) {
const auto ref = coverPageHtml.substr(pos, endPos - pos);
// Check if it's an image file
if (ref.length() >= 4) {
const auto ext = ref.substr(ref.length() - 4);
if (ext == ".png" || ext == ".jpg" || ext == "jpeg" || ext == ".gif") {
imageRef = ref;
break;
}
}
}
pos = coverPageHtml.find(pattern, pos);
}
if (!imageRef.empty()) break;
}
if (!imageRef.empty()) {
bookMetadata.coverItemHref = FsHelpers::normalisePath(coverPageBase + imageRef);
LOG_DBG("EBP", "Found cover image from guide: %s", bookMetadata.coverItemHref.c_str());
}
}
}
bookMetadata.textReferenceHref = opfParser.textReferenceHref;
if (!opfParser.tocNcxPath.empty()) {