PDFBox renderImageWithDPI因字体缺失致内容丢失的解决问询

• 使用PDFBox 2.0.28，后续尝试过PDFBox 3.0.0-RC1
• 通过Loader.loadPDF创建PDDocument
• 基于PDDocument创建PDFRenderer
• 调用renderImageWithDPI(pagenum, dpi, RGBObj)方法
• 获取java.awt.image.BufferedImage对象
• 通过javax.imageio.ImageIO保存为JPG格式
• 生成的图像存在内容丢失问题
• 使用PDFSam basic从原PDF中提取了2个存在问题的样本页面
• 第1页生成的图像中存在内容丢失
• 第2页生成的图像中存在内容丢失
• 已高亮标注图像中的内容丢失区域
• 执行PreflightParser.validate后得到以下校验信息：

1.4 : Trailer Syntax error, /XRef cross reference streams are not allowed
5.2.2 : Forbidden field in an annotation definition, Flags of Link annotation are invalid
2.3.2 : Unexpected value for key in Graphic object definition, Unexpected 'true' value for 'Interpolate' Key
2.4.2 : Invalid Color space, The operator "k" can't be used with RGB Profile
2.4.3 : Invalid Color space, The operator "f" can't be used without Color Profile
3.1.4 : Invalid Font definition, ELWKFI+OptimaLTStd: The Charset entry is missing for the Type1 Subset
3.1.4 : Invalid Font definition, JECWGC+InsigniaLTStd: The Charset entry is missing for the Type1 Subset
3.1.4 : Invalid Font definition, PHSMMZ+OptimaLTStd-Bold: The Charset entry is missing for the Type1 Subset
3.1.4 : Invalid Font definition, EHCNNL+OptimaLTStd-Italic: The Charset entry is missing for the Type1 Subset
3.1.4 : Invalid Font definition, QBVSKF+HelveticaLTStd-Obl: The Charset entry is missing for the Type1 Subset
3.1.9 : Invalid Font definition, UBAPGG+OptimaLTStd: mandatory CIDToGIDMap missing
3.1.11 : Invalid Font definition, UBAPGG+OptimaLTStd: The CIDSet entry is missing for the Composite Subset
3.2.3 : Font damaged, UBAPGG+OptimaLTStd: The FontFile can't be read
3.1.9 : Invalid Font definition, ORMCFE+HelveticaLTStd-Obl: mandatory CIDToGIDMap missing
3.1.11 : Invalid Font definition, ORMCFE+HelveticaLTStd-Obl: The CIDSet entry is missing for the Composite Subset
3.2.3 : Font damaged, ORMCFE+HelveticaLTStd-Obl: The FontFile can't be read
3.1.9 : Invalid Font definition, TFEWKU+HelveticaLTStd-Roman: mandatory CIDToGIDMap missing
3.1.11 : Invalid Font definition, TFEWKU+HelveticaLTStd-Roman: The CIDSet entry is missing for the Composite Subset
3.2.3 : Font damaged, TFEWKU+HelveticaLTStd-Roman: The FontFile can't be read
3.1.4 : Invalid Font definition, CRQQXS+OptimaLTStd: The Charset entry is missing for the Type1 Subset
3.1.4 : Invalid Font definition, MVVAWX+InsigniaLTStd: The Charset entry is missing for the Type1 Subset
3.1.4 : Invalid Font definition, YIWFBD+OptimaLTStd-Bold: The Charset entry is missing for the Type1 Subset
3.1.11 : Invalid Font definition, JYHLHF+OptimaLTStd: The CIDSet entry is missing for the Composite Subset
3.1.9 : Invalid Font definition, LDXBBC+OptimaLTStd: mandatory CIDToGIDMap missing
3.1.11 : Invalid Font definition, LDXBBC+OptimaLTStd: The CIDSet entry is missing for the Composite Subset
3.2.3 : Font damaged, LDXBBC+OptimaLTStd: The FontFile can't be read
3.1.9 : Invalid Font definition, FSNSYC+OptimaLTStd: mandatory CIDToGIDMap missing
3.1.11 : Invalid Font definition, FSNSYC+OptimaLTStd: The CIDSet entry is missing for the Composite Subset
3.2.3 : Font damaged, FSNSYC+OptimaLTStd: The FontFile can't be read
3.1.9 : Invalid Font definition, LVYKUL+InsigniaLTStd: mandatory CIDToGIDMap missing
3.1.11 : Invalid Font definition, LVYKUL+InsigniaLTStd: The CIDSet entry is missing for the Composite Subset
3.2.3 : Font damaged, LVYKUL+InsigniaLTStd: The FontFile can't be read
3.1.9 : Invalid Font definition, FUYTUP+OptimaLTStd-Italic: mandatory CIDToGIDMap missing
3.1.11 : Invalid Font definition, FUYTUP+OptimaLTStd-Italic: The CIDSet entry is missing for the Composite Subset
3.2.3 : Font damaged, FUYTUP+OptimaLTStd-Italic: The FontFile can't be read
3.1.9 : Invalid Font definition, GZVYQO+OptimaLTStd-Bold: mandatory CIDToGIDMap missing
3.1.11 : Invalid Font definition, GZVYQO+OptimaLTStd-Bold: The CIDSet entry is missing for the Composite Subset
3.2.3 : Font damaged, GZVYQO+OptimaLTStd-Bold: The FontFile can't be read
3.1.9 : Invalid Font definition, GWNIWZ+HelveticaLTStd-Roman: mandatory CIDToGIDMap missing
3.1.11 : Invalid Font definition, GWNIWZ+HelveticaLTStd-Roman: The CIDSet entry is missing for the Composite Subset
3.2.3 : Font damaged, GWNIWZ+HelveticaLTStd-Roman: The FontFile can't be read
7.1 : Error on MetaData, Metadata is not a stream

上述校验信息与执行时的警告信息一致：

May 26, 2023 12:40:01 PM org.apache.pdfbox.pdmodel.font.PDCIDFontType2 <init>
WARNING: Could not read embedded OTF for font GWNIWZ+HelveticaLTStd-Roman
java.io.IOException: head is mandatory
    at org.apache.fontbox.ttf.TTFParser.parseTables(TTFParser.java:182)
    at org.apache.fontbox.ttf.TTFParser.parse(TTFParser.java:150)
    at org.apache.fontbox.ttf.OTFParser.parse(OTFParser.java:79)
    at org.apache.fontbox.ttf.OTFParser.parse(OTFParser.java:27)
    at org.apache.fontbox.ttf.TTFParser.parse(TTFParser.java:106)
    at org.apache.fontbox.ttf.OTFParser.parse(OTFParser.java:73)
    at org.apache.pdfbox.pdmodel.font.PDCIDFontType2.<init>(PDCIDFontType2.java:114)
    at org.apache.pdfbox.pdmodel.font.PDCIDFontType2.<init>(PDCIDFontType2.java:67)
    at org.apache.pdfbox.pdmodel.font.PDFontFactory.createDescendantFont(PDFontFactory.java:138)
    at org.apache.pdfbox.pdmodel.font.PDType0Font.<init>(PDType0Font.java:88)
    at org.apache.pdfbox.pdmodel.font.PDFontFactory.createFont(PDFontFactory.java:96)
    at org.apache.pdfbox.pdmodel.PDResources.getFont(PDResources.java:143)
    at org.apache.pdfbox.contentstream.operator.text.SetFontAndSize.process(SetFontAndSize.java:66)
    at org.apache.pdfbox.contentstream.PDFStreamEngine.processOperator(PDFStreamEngine.java:849)
    at org.apache.pdfbox.contentstream.PDFStreamEngine.processStreamOperators(PDFStreamEngine.java:495)
    at org.apache.pdfbox.contentstream.PDFStreamEngine.processStream(PDFStreamEngine.java:469)
    at org.apache.pdfbox.contentstream.PDFStreamEngine.processPage(PDFStreamEngine.java:142)
    at org.apache.pdfbox.rendering.PageDrawer.drawPage(PageDrawer.java:264)
    at org.apache.pdfbox.rendering.PDFRenderer.renderImage(PDFRenderer.java:338)
    at org.apache.pdfbox.rendering.PDFRenderer.renderImage(PDFRenderer.java:259)
    at org.apache.pdfbox.rendering.PDFRenderer.renderImageWithDPI(PDFRenderer.java:245)

其他截断的警告信息：

May 26, 2023 12:40:00 PM org.apache.pdfbox.pdmodel.font.PDCIDFontType2 <init>
WARNING: Could not read embedded OTF for font UBAPGG+OptimaLTStd
java.io.IOException: head is mandatory

May 26, 2023 12:40:01 PM org.apache.pdfbox.pdmodel.font.PDCIDFontType2 <init>
WARNING: Could not read embedded OTF for font GZVYQO+OptimaLTStd-Bold
java.io.IOException: head is mandatory

May 26, 2023 12:40:01 PM org.apache.pdfbox.pdmodel.font.PDCIDFontType2 <init>
WARNING: Could not read embedded OTF for font FUYTUP+OptimaLTStd-Italic
java.io.IOException: head is mandatory

May 26, 2023 12:40:01 PM org.apache.pdfbox.pdmodel.font.PDCIDFontType2 <init>
WARNING: Could not read embedded OTF for font FSNSYC+OptimaLTStd
java.io.IOException: head is mandatory

虽然系统尝试使用备用字体，但仍无法解决问题：

May 26, 2023 12:40:01 PM org.apache.pdfbox.pdmodel.font.PDCIDFontType2 findFontOrSubstitute WARNING: Using fallback font LiberationSans for CID-keyed TrueType font GWNIWZ+HelveticaLTStd-Roman

还出现以下警告信息，不知如何处理：

May 26, 2023 12:40:01 PM org.apache.pdfbox.pdmodel.graphics.color.PDICCBased ensureDisplayProfile WARNING: ICC profile is Perceptual, ignoring, treating as Display class

需要以下两方面技术协助：

问题1：如何正确添加字体？ #

• 尝试以下代码在渲染前为页面添加字体，但无任何效果。
• 注：getDocument()、setDocument和setPdfRenderer是实现类中的便捷方法。*setPdfRenderer()*包含PDFRenderer renderer = new PDFRenderer(document);并将其设置为类变量。

int position = 0;
PDPage page = getDocument().getPage(position);
PDResources resources = page.getResources();
OTFParser otfParser = new OTFParser();
OpenTypeFont otf = otfParser.parse(new File("OptimaLTStd.otf"));
PDFont font = PDType0Font.load(document, otf, false);

resources.add(font);
page.setResources(resources);
if (position == 0) {
   getDocument().getPages().remove(page);
   getDocument().getPages().add(page);
   setDocument(getDocument());
   setPdfRenderer(getDocument());
} else {
   PDPage prevPage = getDocument().getPage(position - 1);
   getDocument().getPages().insertBefore(page, prevPage);
   setDocument(getDocument());
   setPdfRenderer(getDocument());           
}

• 已下载对应OptimaLTStd.otf字体文件

问题2：PDFRenderer是否有重载方法可跳过字形处理，避免字体问题影响图像生成？ #

内容的提问来源于stack exchange，提问作者Mohan