mirror of
https://github.com/Frooodle/Stirling-PDF.git
synced 2025-08-02 13:48:15 +02:00
feat: enhance redaction process with custom font handling and fallback mechanisms in RedactController
This commit is contained in:
Balázs Szücs
parent
8329540e25
commit
314e6c4bc1
@ -308,6 +308,7 @@ public class RedactController {
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if (originalWord == null || originalWord.isEmpty()) {
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return originalWord;
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}
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// Use regular spaces - we'll handle width calculation separately
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return " ".repeat(originalWord.length());
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}
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@ -414,14 +415,37 @@ public class RedactController {
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log.debug("Total pages with found text: {}", allFoundTextsByPage.size());
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// Step 2: Process each page
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// Step 2: Process each page with better font fallback handling
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log.debug("Step 2: Processing each page for text replacement");
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for (PDPage page : document.getPages()) {
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// Replace text content
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List<Object> filteredTokens =
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createTokensWithoutTargetText(
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page, allSearchTerms, useRegex, wholeWordSearchBool);
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writeFilteredContentStream(document, page, filteredTokens);
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boolean fallbackToBoxOnlyMode = false;
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// Check if document uses custom encoding fonts that may cause issues
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boolean hasCustomEncodingFonts = detectCustomEncodingFonts(document);
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if (hasCustomEncodingFonts) {
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log.info(
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"Detected fonts with custom encoding. Using box-only redaction mode to preserve document integrity.");
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fallbackToBoxOnlyMode = true;
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}
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if (!fallbackToBoxOnlyMode) {
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try {
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for (PDPage page : document.getPages()) {
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// Replace text content
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List<Object> filteredTokens =
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createTokensWithoutTargetText(
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page, allSearchTerms, useRegex, wholeWordSearchBool);
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writeFilteredContentStream(document, page, filteredTokens);
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}
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} catch (Exception e) {
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log.warn(
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"Font encoding error encountered during text modification: {}. Falling back to box-only redaction mode.",
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e.getMessage());
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fallbackToBoxOnlyMode = true;
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// Reload the document to reset any partial modifications
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document.close();
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document = pdfDocumentFactory.load(file);
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}
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}
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// Draw redaction boxes for all found texts
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@ -433,6 +457,9 @@ public class RedactController {
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log.debug("Drawing redaction boxes for {} total found texts", allFoundTexts.size());
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if (!allFoundTexts.isEmpty()) {
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if (fallbackToBoxOnlyMode) {
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log.info("Using fallback box-only redaction mode due to font encoding issues");
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}
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redactFoundText(document, allFoundTexts, customPadding, redactColor);
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}
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@ -671,8 +698,11 @@ public class RedactController {
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try {
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float adjustment = calculateWidthAdjustment(segment, segmentMatches);
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tasks.add(new ModificationTask(segment, newText, adjustment));
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} catch (IOException e) {
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log.warn("Failed to calculate width adjustment for redaction.", e);
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} catch (Exception e) {
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log.warn(
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"Failed to calculate width adjustment for redaction due to font encoding issues: {}. Using zero adjustment.",
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e.getMessage());
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tasks.add(new ModificationTask(segment, newText, 0));
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}
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} else if ("TJ".equals(segment.operatorName)) {
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tasks.add(new ModificationTask(segment, null, 0));
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@ -723,62 +753,108 @@ public class RedactController {
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}
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/**
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* Safely calculates the width of a string, handling characters that might not be supported by
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* the font. If a character is not supported, it's replaced with a space or skipped.
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* Safely calculates the width of a string using hardcoded estimates for fonts with custom
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* encoding. This avoids issues with fonts that have non-standard character mappings.
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*/
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private float safeGetStringWidth(PDFont font, String text) throws IOException {
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if (font == null || text == null || text.isEmpty()) {
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return 0;
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}
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StringBuilder safeText = new StringBuilder();
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for (int i = 0; i < text.length(); i++) {
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char c = text.charAt(i);
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try {
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// Try to encode the character to check if it's supported
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font.encode(String.valueOf(c));
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safeText.append(c);
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} catch (IllegalArgumentException e) {
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// If the character is not supported, replace it with a space
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// This is a simple fallback
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safeText.append(' ');
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log.debug(
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"Replaced unsupported character U+{} with space in font {}",
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Integer.toHexString(c | 0x10000).substring(1),
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font.getName());
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try {
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// First, try to get the width directly for standard fonts
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return font.getStringWidth(text);
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} catch (Exception e) {
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log.debug(
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"Font width calculation failed for '{}' in font {}: {}. Using hardcoded width estimation.",
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text,
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font.getName(),
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e.getMessage());
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// Hardcoded width estimation based on font size and character count
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// This provides consistent spacing even with problematic custom encoding fonts
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return getHardcodedStringWidth(text, font);
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}
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}
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/**
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* Provides hardcoded width estimation for text when font metrics are unreliable. Uses average
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* character widths based on font type and character analysis.
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*/
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private float getHardcodedStringWidth(String text, PDFont font) {
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if (text == null || text.isEmpty()) {
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return 0;
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}
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// Determine base character width based on font type
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float baseCharWidth;
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String fontName = font.getName().toLowerCase();
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if (fontName.contains("courier") || fontName.contains("mono")) {
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// Monospace fonts - all characters same width
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baseCharWidth = 600; // Standard monospace width in font units
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} else if (fontName.contains("times") || fontName.contains("serif")) {
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// Serif fonts - slightly narrower average
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baseCharWidth = 450;
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} else {
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// Sans-serif fonts (Arial, Helvetica, etc.) - standard width
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baseCharWidth = 500;
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}
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// Calculate total width with character-specific adjustments
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float totalWidth = 0;
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for (char c : text.toCharArray()) {
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if (c == ' ') {
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totalWidth += baseCharWidth * 0.3f; // Spaces are typically 30% of base width
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} else if (Character.isUpperCase(c)) {
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totalWidth += baseCharWidth * 1.2f; // Uppercase slightly wider
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} else if (c == 'i' || c == 'l' || c == 'j' || c == 'f' || c == 't') {
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totalWidth += baseCharWidth * 0.4f; // Narrow characters
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} else if (c == 'm' || c == 'w' || c == 'W' || c == 'M') {
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totalWidth += baseCharWidth * 1.5f; // Wide characters
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} else {
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totalWidth += baseCharWidth; // Standard width
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}
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}
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return font.getStringWidth(safeText.toString());
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return totalWidth;
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}
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private float calculateWidthAdjustment(TextSegment segment, List<MatchRange> matches)
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throws IOException {
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float totalOriginalWidth = 0;
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float totalPlaceholderWidth = 0;
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String text = segment.getText();
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try {
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float totalOriginalWidth = 0;
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float totalPlaceholderWidth = 0;
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String text = segment.getText();
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for (MatchRange match : matches) {
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int segmentStart = Math.max(0, match.getStartPos() - segment.getStartPos());
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int segmentEnd = Math.min(text.length(), match.getEndPos() - segment.getStartPos());
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for (MatchRange match : matches) {
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int segmentStart = Math.max(0, match.getStartPos() - segment.getStartPos());
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int segmentEnd = Math.min(text.length(), match.getEndPos() - segment.getStartPos());
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if (segmentStart < text.length() && segmentEnd > segmentStart) {
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String originalPart = text.substring(segmentStart, segmentEnd);
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String placeholderPart = createPlaceholder(originalPart);
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if (segmentStart < text.length() && segmentEnd > segmentStart) {
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String originalPart = text.substring(segmentStart, segmentEnd);
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String placeholderPart = createPlaceholder(originalPart);
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if (segment.getFont() != null) {
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totalOriginalWidth +=
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safeGetStringWidth(segment.getFont(), originalPart)
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/ FONT_SCALE_FACTOR
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* segment.getFontSize();
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totalPlaceholderWidth +=
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safeGetStringWidth(segment.getFont(), placeholderPart)
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/ FONT_SCALE_FACTOR
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* segment.getFontSize();
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if (segment.getFont() != null) {
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totalOriginalWidth +=
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safeGetStringWidth(segment.getFont(), originalPart)
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/ FONT_SCALE_FACTOR
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* segment.getFontSize();
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totalPlaceholderWidth +=
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safeGetStringWidth(segment.getFont(), placeholderPart)
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/ FONT_SCALE_FACTOR
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* segment.getFontSize();
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}
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}
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}
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return totalOriginalWidth - totalPlaceholderWidth;
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} catch (Exception e) {
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log.warn(
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"Failed to calculate width adjustment for segment '{}' due to font encoding issues: {}. Skipping adjustment.",
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segment.getText(),
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e.getMessage());
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return 0; // No adjustment when font operations fail
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}
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return totalOriginalWidth - totalPlaceholderWidth;
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}
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private void modifyTokenForRedaction(
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@ -834,71 +910,92 @@ public class RedactController {
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COSArray newArray = createRedactedTJArray((COSArray) token, segment, matches);
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tokens.set(segment.getTokenIndex(), newArray);
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}
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} catch (IOException e) {
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log.warn("Failed to modify token for redaction: {}", e.getMessage(), e);
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} catch (Exception e) {
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log.warn(
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"Failed to modify token for redaction due to font encoding issues: {}. Skipping text modification for segment '{}'.",
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e.getMessage(),
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segment.getText());
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// Don't throw the exception - let the process continue with box-only redaction
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}
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}
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private COSArray createRedactedTJArray(
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COSArray originalArray, TextSegment segment, List<MatchRange> matches)
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throws IOException {
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COSArray newArray = new COSArray();
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int textOffsetInSegment = 0;
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try {
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COSArray newArray = new COSArray();
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int textOffsetInSegment = 0;
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for (COSBase element : originalArray) {
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if (element instanceof COSString cosString) {
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String originalText = cosString.getString();
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StringBuilder newText = new StringBuilder(originalText);
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boolean modified = false;
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for (COSBase element : originalArray) {
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if (element instanceof COSString cosString) {
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String originalText = cosString.getString();
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StringBuilder newText = new StringBuilder(originalText);
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boolean modified = false;
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for (MatchRange match : matches) {
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int stringStartInPage = segment.getStartPos() + textOffsetInSegment;
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int stringEndInPage = stringStartInPage + originalText.length();
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for (MatchRange match : matches) {
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int stringStartInPage = segment.getStartPos() + textOffsetInSegment;
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int stringEndInPage = stringStartInPage + originalText.length();
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int overlapStart = Math.max(match.getStartPos(), stringStartInPage);
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int overlapEnd = Math.min(match.getEndPos(), stringEndInPage);
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int overlapStart = Math.max(match.getStartPos(), stringStartInPage);
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int overlapEnd = Math.min(match.getEndPos(), stringEndInPage);
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if (overlapStart < overlapEnd) {
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modified = true;
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int redactionStartInString = overlapStart - stringStartInPage;
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int redactionEndInString = overlapEnd - stringStartInPage;
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if (redactionStartInString >= 0
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&& redactionEndInString <= originalText.length()) {
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String placeholder =
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createPlaceholder(
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originalText.substring(
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redactionStartInString, redactionEndInString));
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newText.replace(
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redactionStartInString, redactionEndInString, placeholder);
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if (overlapStart < overlapEnd) {
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modified = true;
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int redactionStartInString = overlapStart - stringStartInPage;
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int redactionEndInString = overlapEnd - stringStartInPage;
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if (redactionStartInString >= 0
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&& redactionEndInString <= originalText.length()) {
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String placeholder =
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createPlaceholder(
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originalText.substring(
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redactionStartInString,
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redactionEndInString));
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newText.replace(
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redactionStartInString, redactionEndInString, placeholder);
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}
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}
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}
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}
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String modifiedString = newText.toString();
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newArray.add(new COSString(modifiedString));
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String modifiedString = newText.toString();
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newArray.add(new COSString(modifiedString));
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if (modified && segment.getFont() != null && segment.getFontSize() > 0) {
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float originalWidth =
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safeGetStringWidth(segment.getFont(), originalText)
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/ FONT_SCALE_FACTOR
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* segment.getFontSize();
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float modifiedWidth =
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safeGetStringWidth(segment.getFont(), modifiedString)
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/ FONT_SCALE_FACTOR
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* segment.getFontSize();
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float adjustment = originalWidth - modifiedWidth;
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if (Math.abs(adjustment) > PRECISION_THRESHOLD) {
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float kerning = -FONT_SCALE_FACTOR * adjustment / segment.getFontSize();
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newArray.add(new org.apache.pdfbox.cos.COSFloat(kerning));
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if (modified && segment.getFont() != null && segment.getFontSize() > 0) {
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try {
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float originalWidth =
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safeGetStringWidth(segment.getFont(), originalText)
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/ FONT_SCALE_FACTOR
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* segment.getFontSize();
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float modifiedWidth =
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safeGetStringWidth(segment.getFont(), modifiedString)
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/ FONT_SCALE_FACTOR
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* segment.getFontSize();
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float adjustment = originalWidth - modifiedWidth;
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if (Math.abs(adjustment) > PRECISION_THRESHOLD) {
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float kerning =
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-FONT_SCALE_FACTOR * adjustment / segment.getFontSize();
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newArray.add(new org.apache.pdfbox.cos.COSFloat(kerning));
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}
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} catch (Exception e) {
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log.warn(
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"Failed to calculate kerning adjustment for TJ array element due to font encoding issues: {}. Skipping adjustment.",
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e.getMessage());
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// Continue without kerning adjustment
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}
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}
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}
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textOffsetInSegment += originalText.length();
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} else {
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newArray.add(element);
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textOffsetInSegment += originalText.length();
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} else {
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newArray.add(element);
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}
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}
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return newArray;
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} catch (Exception e) {
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log.warn(
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"Failed to create redacted TJ array due to font encoding issues: {}. Returning original array.",
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e.getMessage());
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// Return the original array if we can't modify it safely
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return originalArray;
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}
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return newArray;
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}
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private String extractTextFromToken(Object token, String operatorName) {
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@ -924,4 +1021,58 @@ public class RedactController {
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default -> "";
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};
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}
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/**
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* Detects if the document contains fonts with custom encoding that may cause text modification
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* issues. Custom encoding fonts often have internal character mappings that don't follow
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* Unicode standards.
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*/
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private boolean detectCustomEncodingFonts(PDDocument document) {
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try {
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for (PDPage page : document.getPages()) {
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PDResources resources = page.getResources();
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if (resources != null) {
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for (COSName fontName : resources.getFontNames()) {
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try {
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PDFont font = resources.getFont(fontName);
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if (font != null) {
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String name = font.getName();
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// Check for font names that commonly indicate custom encoding
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if (name != null
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&& (name.contains("HOEP")
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|| // Common custom encoding prefix
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name.contains("+")
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|| // Subset fonts often have custom encoding
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name.matches(".*[A-Z]{6}\\+.*") // Six letter prefix
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// pattern
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)) {
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log.debug("Detected potential custom encoding font: {}", name);
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// Try a simple encoding test
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try {
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font.encode(" "); // Test space character
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font.getStringWidth(" ");
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} catch (Exception e) {
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log.debug(
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"Font {} failed basic encoding test: {}",
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name,
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e.getMessage());
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return true;
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}
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}
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}
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} catch (Exception e) {
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log.debug(
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"Error checking font for custom encoding: {}", e.getMessage());
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}
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}
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}
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}
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return false;
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} catch (Exception e) {
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log.warn(
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"Error detecting custom encoding fonts: {}. Assuming custom encoding present.",
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e.getMessage());
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return true; // Err on the side of caution
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}
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}
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}
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