PDFlib 8 Windows COM/.NET Tutorial

String optlist13 =
"OPI-1.3 { ALDImageFilename bigfile.tif " +
"ALDImageDimensions {400 561} " +
"ALDImageCropRect {10 10 390 550} " +
"ALDImagePosition {10 10 10 540 390 540 390 10} }";
image = p.load_image("tiff", filename, optlist13);
Note Some OPI servers, such as the one included in Helios EtherShare, do not properly implement OPI
processing for PDF Image XObjects, which PDFlib generates by default. In such cases generation
of Form XObjects can be forced by supplying the template option to load_image( ).
XMP metadata in images. Image files may contain XMP metadata. By default PDFlib
ignores image metadata for images in the TIFF, JPEG, and JPEG 2000 image formats to
reduce the output file size. However, the XMP metadata can be attached to the generated
image in the output PDF document with the following option of load_image( ):
metadata={keepxmp=true}
7.1.2 Supported Image File Formats
PDFlib deals with the image file formats described below. By default, PDFlib passes the
compressed image data unchanged to the PDF output if possible since PDF internally
supports most compression schemes used in common image file formats. This technique
(called pass-through mode in the descriptions below) results in very fast image import,
since decompressing the image data and subsequent recompression are not necessary.
However, PDFlib cannot check the integrity of the compressed image data in this
mode. Incomplete or corrupt image data may result in error or warning messages when
using the PDF document in Acrobat (e.g., Read less image data than expected). Passthrough
mode can be controlled with the passthrough option of load_image( ).
If an image file can’t be imported successfully load_image( ) will return an error code.
If you need to know more details about the image failure, call get_errmsg( ) to retrieve a
detailed error message.
PNG images. PDFlib supports all flavors of PNG images (ISO 15948). PNG images are
handled in pass-through mode in most cases. If a PNG image contains transparency information,
the transparency is retained in the generated PDF (see Section 7.1.4, »Image
Masks and Transparency«, page 184).
JPEG images. JPEG images (ISO 10918-1) are never decompressed, but some flavors may
require transcoding for proper display in Acrobat. PDFlib automatically applies transcoding
to certain types of JPEG images, but transcoding can also be controlled via the
passthrough option of load_image( ). Transcoding does not change the pixel count or color
of an image, and does not introduce any visible compression/decompression artifacts.
PDFlib supports the following JPEG image flavors:
> Grayscale, RGB (usually encoded as YCbCr), and CMYK color
> Baseline JPEG compression which accounts for the vast majority of JPEG images.
> Progressive JPEG compression.
JPEG images can be packaged in several different file formats. PDFlib supports all common
JPEG file formats, and will read resolution information from the following flavors:
> JFIF, which is generated by a wide variety of imaging applications.
7.1 Importing Raster Images 181