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age contains transparency information, the transparency is retained in the generatedPDF (see Section 6.1.4, »Image Masks and Transparency«, page 125). However, alphachannels are not supported by PDFlib.JPEG images. JPEG images (ISO 10918-1) are never decompressed, but some flavors mayrequire transcoding for proper display in Acrobat. PDFlib automatically applies transcodingto certain critical types of JPEG images, but transcoding can also be controlledvia the passthrough option of PDF_load_image( ). PDFlib supports the following JPEG imageflavors:> 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 commonJPEG file formats, and will read resolution information from the following flavors:> JFIF, which is generated by a wide variety of imaging applications.> JPEG files written by Adobe Photoshop and other Adobe applications. PDFlib appliesa workaround which is necessary to correctly process Photoshop-generated CMYKJPEG files. PDFlib will also read clipping paths from JPEG images created with AdobePhotoshop.Note PDFlib does not interpret color space or resolution information from JPEG images in the SPIFFor Exif formats.JPEG2000 images. JPEG2000 images (ISO 15444-2) require PDF 1.5 or above, and are alwayshandled in pass-through mode. PDFlib supports JPEG2000 images as follows:> JP2 and JPX baseline images (usually *.jp2 or *.jpf) are supported, subject to the colorspace conditions below. All valid color depth values are supported.> The following color spaces are supported: sRGB, sRGB-grey, ROMM-RGB, sYCC,e-sRGB, e-sYCC, CIELab, ICC-based color spaces (restricted and full ICC profile), andCMYK. PDFlib will not alter the original color space in the JPEG2000 image file.> Images containing a soft mask can be used with the mask option to prepare a maskwhich can be applied to other images.> External ICC profiles can not be applied to a JPEG2000 image, i.e. the iccprofile optionmust not be used. ICC profiles contained in the JPEG2000 image file will always bekept, i.e. the honoriccprofile option is always true.> The colorize option is not supported for JPEG2000 images.Note Raw JPEG2000 code streams without JPX wrapper (often *.j2k) and JPM compound image filesaccording to ISO 15444-6 (usually *.jpm) are not supported.GIF images. PDFlib supports all GIF flavors (specifically GIF 87a and 89a) with interlacedand non-interlaced pixel data and all palette sizes. GIF images will always be recompressedwith Flate compression.TIFF images. PDFlib will handle most TIFF images in pass-through mode. PDFlib supportsthe following flavors of TIFF images:> compression schemes: uncompressed, CCITT (group 3, group 4, and RLE), ZIP (=Flate),and PackBits (=RunLength) are handled in pass-through mode; other compressionschemes, such as LZW and JPEG, are handled by uncompressing.6.1 Importing Raster Images 123