Question

我想知道一种提取单独措施的方法。我不确定这个算法是否已经存在，所以我想到从左到右扫描乐谱，从一行测量的上方和下方提取所有的空白区域。

我不是在寻找将乐谱转换为MusicXML或提取其他有用信息的方法。不，基本上我正在处理的是一份常规文件。我需要分开段落。我对该段所传达的信息不感兴趣，只是简单地将它们与文件的各个区域分开。在这种情况下，一个段落将是一行措施。我并不需要单独的措施，而是每张乐谱的所有措施。

enter image description here

这是我想从完整的乐谱中输出但没有标题，作曲家等的输出之一。 enter image description here

Answer 1

假设您在PDF文件中有乐谱，我会使用Apache PDFBox从包含乐谱的输入PDF文件中获取图像，然后找到所需的整个条形图的坐标，使用所选图像定义坐标以裁剪图像并对其进行操作，直到获得所需的结果。

PDDocument document = null; 
document = PDDocument.load(inFile); 
List pages = document.getDocumentCatalog().getAllPages();
Iterator iter = pages.iterator(); 
while (iter.hasNext()) {
            PDPage page = (PDPage) iter.next();
            PDResources resources = page.getResources();
            Map pageImages = resources.getImages();
            if (pageImages != null) { 
                Iterator imageIter = pageImages.keySet().iterator();
                while (imageIter.hasNext()) {
                    String key = (String) imageIter.next();
                    PDXObjectImage image = (PDXObjectImage) pageImages.get(key);
                    image.write2OutputStream(/* some output stream */);
                }
            }
}

以下是Apache PDFBox中提供的示例代码。

import java.io.File;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDResources;
import org.apache.pdfbox.pdmodel.encryption.AccessPermission;
import org.apache.pdfbox.pdmodel.encryption.StandardDecryptionMaterial;
import org.apache.pdfbox.pdmodel.graphics.xobject.PDXObject;
import org.apache.pdfbox.pdmodel.graphics.xobject.PDXObjectForm;
import org.apache.pdfbox.pdmodel.graphics.xobject.PDXObjectImage;

/**
 * This will read a read pdf and extract images. <br/><br/>
 *
 * usage: java org.apache.pdfbox.ExtractImages &lt;pdffile&gt; &lt;password&gt; [imageprefix]
 *
 * @author  <a href="mailto:ben@benlitchfield.com">Ben Litchfield</a>
 * @version $Revision: 1.7 $
 */
public class ExtractImages
{
    private int imageCounter = 1;

    private static final String PASSWORD = "-password";
    private static final String PREFIX = "-prefix";
    private static final String ADDKEY = "-addkey";
    private static final String NONSEQ = "-nonSeq";

    private ExtractImages()
    {
    }

    /**
     * This is the entry point for the application.
     *
     * @param args The command-line arguments.
     *
     * @throws Exception If there is an error decrypting the document.
     */
    public static void main( String[] args ) throws Exception
    {
        ExtractImages extractor = new ExtractImages();
        extractor.extractImages( args );
    }

    private void extractImages( String[] args ) throws Exception
    {
        if( args.length < 1 || args.length > 4 )
        {
            usage();
        }
        else
        {
            String pdfFile = null;
            String password = "";
            String prefix = null;
            boolean addKey = false;
            boolean useNonSeqParser = false;
            for( int i=0; i<args.length; i++ )
            {
                if( args[i].equals( PASSWORD ) )
                {
                    i++;
                    if( i >= args.length )
                    {
                        usage();
                    }
                    password = args[i];
                }
                else if( args[i].equals( PREFIX ) )
                {
                    i++;
                    if( i >= args.length )
                    {
                        usage();
                    }
                    prefix = args[i];
                }
                else if( args[i].equals( ADDKEY ) )
                {
                    addKey = true;
                }
                else if( args[i].equals( NONSEQ ) )
                {
                    useNonSeqParser = true;
                }
                else
                {
                    if( pdfFile == null )
                    {
                        pdfFile = args[i];
                    }
                }
            }
            if(pdfFile == null)
            {
                usage();
            }
            else
            {
                if( prefix == null && pdfFile.length() >4 )
                {
                    prefix = pdfFile.substring( 0, pdfFile.length() -4 );
                }

                PDDocument document = null;

                try
                {
                    if (useNonSeqParser)
                    {
                        document = PDDocument.loadNonSeq(new File(pdfFile), null, password);
                    }
                    else
                    {
                        document = PDDocument.load( pdfFile );

                        if( document.isEncrypted() )
                        {
                            StandardDecryptionMaterial spm = new StandardDecryptionMaterial(password);
                            document.openProtection(spm);
                        }
                    }
                    AccessPermission ap = document.getCurrentAccessPermission();
                    if( ! ap.canExtractContent() )
                    {
                        throw new IOException(
                            "Error: You do not have permission to extract images." );
                    }

                    List pages = document.getDocumentCatalog().getAllPages();
                    Iterator iter = pages.iterator();
                    while( iter.hasNext() )
                    {
                        PDPage page = (PDPage)iter.next();
                        PDResources resources = page.getResources();
                        // extract all XObjectImages which are part of the page resources
                        processResources(resources, prefix, addKey);
                    }
                }
                finally
                {
                    if( document != null )
                    {
                        document.close();
                    }
                }
            }
        }
    }

    private void processResources(PDResources resources, String prefix, boolean addKey) throws IOException
    {
        if (resources == null)
        {
            return;
        }
        Map<String, PDXObject> xobjects = resources.getXObjects();
        if( xobjects != null )
        {
            Iterator<String> xobjectIter = xobjects.keySet().iterator();
            while( xobjectIter.hasNext() )
            {
                String key = xobjectIter.next();
                PDXObject xobject = xobjects.get( key );
                // write the images
                if (xobject instanceof PDXObjectImage)
                {
                    PDXObjectImage image = (PDXObjectImage)xobject;
                    String name = null;
                    if (addKey) 
                    {
                        name = getUniqueFileName( prefix + "_" + key, image.getSuffix() );
                    }
                    else 
                    {
                        name = getUniqueFileName( prefix, image.getSuffix() );
                    }
                    System.out.println( "Writing image:" + name );
                    image.write2file( name );
                }
                // maybe there are more images embedded in a form object
                else if (xobject instanceof PDXObjectForm)
                {
                    PDXObjectForm xObjectForm = (PDXObjectForm)xobject;
                    PDResources formResources = xObjectForm.getResources();
                    processResources(formResources, prefix, addKey);
                }
            }
        }
    }

    private String getUniqueFileName( String prefix, String suffix )
    {
        String uniqueName = null;
        File f = null;
        while( f == null || f.exists() )
        {
            uniqueName = prefix + "-" + imageCounter;
            f = new File( uniqueName + "." + suffix );
            imageCounter++;
        }
        return uniqueName;
    }

    /**
     * This will print the usage requirements and exit.
     */
    private static void usage()
    {
        System.err.println( "Usage: java org.apache.pdfbox.ExtractImages [OPTIONS] <PDF file>\n" +
            "  -password  <password>        Password to decrypt document\n" +
            "  -prefix  <image-prefix>      Image prefix(default to pdf name)\n" +
            "  -addkey                      add the internal image key to the file name\n" +
            "  -nonSeq                      Enables the new non-sequential parser\n" +
            "  <PDF file>                   The PDF document to use\n"
            );
        System.exit( 1 );
    }

}

现在可以使用裁剪图像：

/**
     * Crop the main image according to this rectangle, and scale it to the
     * correct size for a thumbnail.
     */
    public InputStream cropAndScale(InputStream mainImageStream,
            CropRectangle crop) {
        try {
            RenderedOp mainImage = loadImage(mainImageStream);
            RenderedOp opaqueImage = makeImageOpaque(mainImage);
            RenderedOp croppedImage = cropImage(opaqueImage, crop);
            RenderedOp scaledImage = scaleImage(croppedImage);
            byte[] jpegBytes = encodeAsJpeg(scaledImage);
            return new ByteArrayInputStream(jpegBytes);
        } catch (Exception e) {
            throw new IllegalStateException("Failed to scale the image", e);
        }
    }

可在this page和project

中找到

还有其他选项可以解析pdf文件中的图像，请特别查看at this code this

从乐谱中提取每一行的度量

1 个答案: