fix: preserve images in dark reader theme

Sources/RDEpubReaderView/EPUBUI/TextPage/RDEPUBDarkImageAdjuster.swift

@@ -5,22 +5,6 @@ import DTCoreText
 #endif
 
 enum RDEPUBDarkImageAdjuster {
-
-    private static let imageCache: NSCache<NSString, UIImage> = {
-        let cache = NSCache<NSString, UIImage>()
-        cache.countLimit = 100
-        cache.totalCostLimit = 52_428_800  // 50 MB
-        return cache
-    }()
-
-    private static func imageCost(of image: UIImage) -> Int {
-        let scale = image.scale
-        let width = Int(image.size.width * scale)
-        let height = Int(image.size.height * scale)
-        // 4 bytes per pixel (RGBA)
-        return width * height * 4
-    }
-
 #if canImport(DTCoreText)
 
     static func adjustIfNeeded(
@@ -28,80 +12,13 @@ enum RDEPUBDarkImageAdjuster {
         in range: NSRange? = nil,
         configuration: RDEPUBReaderConfiguration
     ) -> NSMutableAttributedString {
-        guard configuration.darkImageAdjustmentEnabled,
+        // DTCoreText retains rendering state on its original image attachment.
-              configuration.darkImageBlendRatio > 0,
+        // Replacing that attachment with a newly rendered UIImage preserves its
-              configuration.theme.contentBackgroundColor.rd_isDarkBackground else {
+        // layout size but can leave its drawing callback empty in dark mode.
-            return content
+        // Keep the original attachment until image dimming can be performed
-        }
+        // without changing the attachment instance.
-
-        let fullRange = NSRange(location: 0, length: content.length)
-        let targetRange = range.map { NSIntersectionRange($0, fullRange) } ?? fullRange
-        content.enumerateAttribute(.attachment, in: targetRange) { value, range, _ in
-            guard let attachment = value as? DTImageTextAttachment,
-                  !isCoverAttachment(attachment),
-                  let image = attachment.image,
-                  shouldAdjust(image) else { return }
-
-            let adjustedAttachment = DTImageTextAttachment()
-            adjustedAttachment.image = adjustedImage(
-                image,
-                backgroundColor: configuration.theme.contentBackgroundColor,
-                blendRatio: configuration.darkImageBlendRatio,
-                cacheKey: cacheKey(for: attachment, image: image, configuration: configuration)
-            )
-            adjustedAttachment.originalSize = attachment.originalSize
-            adjustedAttachment.displaySize = attachment.displaySize
-            adjustedAttachment.verticalAlignment = attachment.verticalAlignment
-            adjustedAttachment.contentURL = attachment.contentURL
-            adjustedAttachment.hyperLinkURL = attachment.hyperLinkURL
-            adjustedAttachment.hyperLinkGUID = attachment.hyperLinkGUID
-            adjustedAttachment.attributes = attachment.attributes
-            content.addAttribute(.attachment, value: adjustedAttachment, range: range)
-        }
         return content
     }
 
-    private static func isCoverAttachment(_ attachment: DTTextAttachment) -> Bool {
-        let lowercasedClasses = ((attachment.attributes["class"] as? String) ?? "").lowercased()
-        let lowercasedPath = attachment.contentURL?.lastPathComponent.lowercased()
-            ?? ((attachment.attributes["src"] as? String) ?? "").lowercased()
-        return lowercasedClasses.contains("rd-front-cover-image") || lowercasedPath.contains("cover")
-    }
-
-    private static func shouldAdjust(_ image: UIImage) -> Bool {
-        image.size.width >= 80 && image.size.height >= 80
-    }
-
-    private static func cacheKey(
-        for attachment: DTImageTextAttachment,
-        image: UIImage,
-        configuration: RDEPUBReaderConfiguration
-    ) -> NSString {
-        let source = attachment.contentURL?.absoluteString
-            ?? "\(Unmanaged.passUnretained(image).toOpaque())"
-        return "\(source)|\(image.size.width)x\(image.size.height)|\(configuration.theme.contentBackgroundColor.rd_cssString)|\(configuration.darkImageBlendRatio)" as NSString
-    }
-
-    private static func adjustedImage(
-        _ image: UIImage,
-        backgroundColor: UIColor,
-        blendRatio: CGFloat,
-        cacheKey: NSString
-    ) -> UIImage {
-        if let cached = imageCache.object(forKey: cacheKey) { return cached }
-        let format = UIGraphicsImageRendererFormat()
-        format.scale = image.scale
-        format.opaque = false
-        let renderer = UIGraphicsImageRenderer(size: image.size, format: format)
-        let adjusted = renderer.image { context in
-            image.draw(in: CGRect(origin: .zero, size: image.size))
-            backgroundColor.withAlphaComponent(max(0, min(0.35, blendRatio))).setFill()
-            context.cgContext.setBlendMode(.sourceAtop)
-            context.fill(CGRect(origin: .zero, size: image.size))
-        }
-        imageCache.setObject(adjusted, forKey: cacheKey, cost: imageCost(of: adjusted))
-        return adjusted
-    }
-
 #endif
 }