Implementing PDF Features

Overview:

The PDF module enhances the input/output functionality in LEADTOOLS by supporting a number of powerful and complex file formats including:

PDF is emerging as a powerful format for reproducing documents over the web. Because of its high precision and accuracy in representing text and pictures along with its "hyper" nature, PDF is becoming a popular alternative to HTML and Postscript.

Loading Capabilities:

LEADTOOLS PDF has the following import capabilities:

  1. Loads essentially all PDF 1.3 (Acrobat 4.x compatible) through PDF 1.7 files.

  2. Loads all PostScript Language Level 3 files.

  3. Loads any EPS file.

Loading support includes multi-threading support and multi-page support, where you can specify which page or range of pages to load from the file.

LEADTOOLS gives you a number of control options in order to customize the rasterized page. These options include:

  1. Pixel depth. Valid values are 0 (for auto-detect) 1, 4, 8 and 24. The default value for this control parameter is 24.

  2. Horizontal and vertical resolution in dots per inch with a default value of 96 by 96. It is recommended you change these to 300 if your application is loading the PDF files for recognition purposes (OCR or barcode for example) by using CodecsRasterizeDocumentLoadOptions.

  3. Font anti-aliasing. Valid values are 1bit (no anti-aliasing), 2 and 4-bit anti-aliasing. The default value is 1, which gives the sharpest representation of the text in the file.

  4. Graphics anti-aliasing. Valid values are 1bit (no anti-aliasing), 2 and 4-bit anti-aliasing. The default value is 1.

Use CodecsPdfOptions to set control options for loading a file.

Use the RasterCodecs.GetRasterPdfInfo method to get information specific to a PDF file on disk or in a stream. Such information includes its original bits/pixel, compression, size and resolution.

Saving Capabilities:

Full multi-page write support is provided by LEADTOOLS for the PDF format. You can append, insert, replace or delete specific pages in a PDF file created by LEADTOOLS.

LEADTOOLS PDF gives you a wide range of control options for the resulting image data in terms of compression, including:

  1. No compression.

  2. Compressed using CCITT Group 3, 1 dimension. For 1-bit images.

  3. Compressed using CCITT Group 3, 2 dimensions. For 1-bit images.

  4. Compressed using CCITT Group 4. For 1-bit images.

  5. JPEG compression and YUV 4:4:4 color space loss-less. Bits per pixel: 8 for grayscale, 24 for color.

  6. JPEG compression and YUV 4:2:2 color space. Bits per pixel: 8 for grayscale, 24 for color.

  7. JPEG compression and YUV 4:1:1 color space. Bits per pixel: 8 for grayscale, 24 for color.

A number of save format constants are provided to support types of files created by LEADTOOLS. For a list of these, please refer to Summary of All Supported Image File Formats.

LEADTOOLS also gives you control over the type of encoding to be used in order to change compressed image data into a text format. The text encoding techniques include:

  1. No text encoding at all.

  2. Use ASCII 85 text encoding algorithm.

  3. Use ASCII HEX text encoding technique.

In order to specify which type of text encoding to use when saving, refer to TextEncoding.

LEAD provides the CodecsPdfOptions.Save property in order to specify which type of text encoding to use when saving and to let you control the security of and access to the PDF file that is saved. These include user and owner passwords, encryption options, and the capabilities the user of the resulting PDF document will have. To determine or set the current options used when saving a PDF file use CodecsOptions.Save.

Distributing an application built using the LEADTOOLS PDF SDK

To load or save PDF documents to/from a raster image in LEADTOOLS, use the Leadtools.Pdf.dll assembly. This is the file filter for the PDF format (as well as Postscript and Enhanced Postscript). Use this assembly as any other file filter in LEADTOOLS, such as Leadtools.Codecs.Bmp.dll for BMP support or Leadtools.Codecs.Tif.dll for TIF support.

In addition to Leadtools.Pdf.dll, the Leadtools.Pdf.Utilities.dll assembly is required in the following situations:

Leadtools.Pdf.Utilities.dll contains many resources such as tables and fonts required to render a PDF image (if one of the options above is satisfied and also always for PS and EPS files). This DLL is not referenced in a direct way by the file filter; instead it is loaded dynamically and out of a process if needed. You must ensure that this DLL is present on the machine. By default, it is required to have this DLL in the same directory where the file filter is located. However, to share many instances of the Leadtools.Pdf.Utilities.dll assembly between many applications, use the CodecsPdfOptions.InitialPath property.

Note that when an application is only loading and saving PDF files as raster images, the PDF Engine is not required. In such cases, the Leadtools.Pdf.Utilities.dll is not required to be present on the machine. Leadtools.Pdf.dll is always required, regardless.

In addition to these DLLs, other DLLS may be needed when saving PDF files because of the compression used. For more information, refer to Files To Be Included With Your Application.

PDF Support

RasPdf, RasPdfLzw, RasPdfG31Dim, RasPdfG32Dim, RasPdfG4, RasPdfJbig2, RasPdfJpeg, RasPdfJpeg422, RasPdfJpeg411, RasPdfCmyk, RasPdfLzwCmyk, and RasPdfJpx formats require, in addition to the Leadtools.dll, the following DLLs: Leadtools.Codecs.dll, Leadtools.Codecs.Fax.dll, and Leadtools.Color.Conversion.dll.

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