A CiPdf object is associated with a CiImage object.  It allows to set/get parameters controlling functionality CiImage.Open, CiImage.SaveAs and CiImage.Append methods while working with PDF files.

CiImage.SaveAs method writes metadata to PDF from Author, Creator, Keywords, Subject, Title, ModDate properties.
CiImage.Open method obtains Author, Creator, Keywords, Subject, Title, CreationDate, Producer properties from PDF file metadata.

A PDF file encapsulates the various type of data:  images, text, graphics, annotation, etc.   Many applications generate PDF pages containing textual and graphics data.  Such pages are rasterized to obtain page image. Scanners and imaging system store multi-page images in a PDF file, as a substitute for multi-page TIFF format.   Such images can be extracted directly from PDF file.  

To obtain an image of "non-image" content PDF pages, like text, graphic, annotation (including annotation-based barcodes) PDF page has to be rasterized.  Rasterization is similar to taking a snapshot of a page as displayed by the PDF viewer. 

CiImage.Open method uses the value of the readMode property to treat PDF file as a collection of image,  a collection of rasterized pages or the mix of those.  

• If readMode = epemImage,  Open method locates images encapsulated in PDF file.
  If the image dimensions are less then minImageWidth and minImageHeight (expressed in inches, ignored if 0.0) it is skipped. 
  Some scanners store black-and-white images inside of PDF using color format.   Set useMinImageColors to ciTrue to improve the efficiency of image processing by converting the image to the minimum needed number of color needed, i.e., grayscale or black-and-white.
• If readMode = epemRaster,   Open method rasterizes each page.   The color of the resulting image is determined by the rasterColorMode property.  If it is set to eprmAuto color is based on colors present on the page.    eprmAuto mode is slower than specific color setting.   Resolution of the rasterized image is specified separately for each of 3 modes: Black-and-white, grayscale, and RGB defined by values of dpiRasterBw, dpiRasterGs, dpiRasterRgb respectively.
• If readMode = epemAuto,   Open method analyzes each page of PDF file for the presence of an image, occupying 90% of the page.  If such an image is present, this page is considered an image page and image is extracted, otherwise, the page is rasterized.  Mixed Raster Content (MRC) compressed images are also rasterized. 

See PDF files guidelines on Inlite's How-to Web Site

CiPdf Members