使用iText从PDF坐标中提取图像

Question

有可能吗？如果是，那么它可以怎么做。

Answer 1

按照iText示例ExtractImages的思路，您可以像下面这样提取代码：

PdfReader reader = new PdfReader(resourceStream);
PdfReaderContentParser parser = new PdfReaderContentParser(reader);
ImageRenderListener listener = new ImageRenderListener("testpdf");

for (int i = 1; i <= reader.getNumberOfPages(); i++) {
    parser.processContent(i, listener);
}

ImageRenderListener的定义如下：

class ImageRenderListener implements RenderListener
{
    final String name;
    int counter = 100000;

    public ImageRenderListener(String name)
    {
        this.name = name;
    }

    public void beginTextBlock() { }
    public void renderText(TextRenderInfo renderInfo) { }
    public void endTextBlock() { }

    public void renderImage(ImageRenderInfo renderInfo)
    {
        try
        {
            PdfImageObject image = renderInfo.getImage();
            if (image == null) return;
            int number = renderInfo.getRef() != null ? renderInfo.getRef().getNumber() : counter++;
            String filename = String.format("%s-%s.%s", name, number, image.getFileType());
            FileOutputStream os = new FileOutputStream(filename);
            os.write(image.getImageAsBytes());
            os.flush();
            os.close();

            PdfDictionary imageDictionary = image.getDictionary();
            PRStream maskStream = (PRStream) imageDictionary.getAsStream(PdfName.SMASK);
            if (maskStream != null)
            {
                PdfImageObject maskImage = new PdfImageObject(maskStream);
                filename = String.format("%s-%s-mask.%s", name, number, maskImage.getFileType());
                os = new FileOutputStream(filename);
                os.write(maskImage.getImageAsBytes());
                os.flush();
                os.close();
            }
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
    }
}

如您所见，ImageRenderListener方法RenderImage检索参数ImageRenderInfo。这个参数有方法

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