Image File Types and Associated Attributes

Attributes for Reading Image Files

The table below describes the attributes that you can specify for the image readers.

When you are reading images, include the FORMAT= attribute in the method if any of the following conditions are true:

You are reading a format that is supported only on certain hosts.
The images reside in SAS catalogs.
The images are being read from a system pipe.

FORMAT= is not required in other cases, but it is always more efficient to specify it.

Image Formats for Reading

File Type

Reader Attributes

Comment

BMP

FORMAT=BMP

COMPRESS=NONE

COMPRESS=RLE

is the default.

sets compression to run-length encoded.

CAT

FORMAT=CAT

DIB

FORMAT=DIB

is supported only by Windows 3.1, Windows 95, Windows 98, Windows 2000 and Windows NT.

EMF

FORMAT=EMF

is supported only by Windows 95, Windows 98, Windows 2000, and Windows NT.

EPSI

FORMAT=EPSI

DPI=num

When read with the Image Editor, the SAS/AF Image DataModel, or IMGOP, EPSI files are displayed using a low-resolution, monochrome preview of the actual image.

specifies the number of dots per inch when the output file is created.

GIF

FORMAT=GIF

JFIF

FORMAT=JFIF

is required for reading JPEG files that use JPEG File Interchange Format (JFIF).

DCT=mode

selects the specific type of Discrete Cosine Transform (DCT) to use when processing the image; mode can be

INT -- an integer DCT
FAST -- a faster and less accurate integer DCT
FLOAT -- a slightly more accurate method that can be slower unless the host has very fast floating-point hardware.

GRAYSCALE

produces a gray-scale image even if the JPEG file is in color. This is useful for viewing on monochrome displays. The reader runs noticeably faster in this mode.

VERSION

prints the version number and copyright messages for the Independent JPE Group's JFIF software to the log.

FAST

enables certain recommended processing options for fast, low quality output; equivalent to enabling ONEPASS, DITHER=ORDERED, COLORS=216, NOSMOOTH, and DCT=FAST.

NOSMOOTH

uses a faster, lower quality, upsampling routine.

ONEPASS

uses a one-pass color quantization instead of the standard two-pass quantization. The one-pass method is faster and needs less memory, but it produces a lower-quality image. This attribute is ignored unless you also specify the COLORS attribute. ONEPASS is always enabled for gray-scale output.

COLORS=n

reduces the number of colors in the image to at most n colors; n must be in the range 2...256.

SCALE_RATIO=n

scales the output image by a factor of 1/n. Currently the scale factor must be 1/1, 1/2, 1/4, or 1/8. This is useful when processing a large image and only a smaller version is needed, because the reader is much faster when scaling down the output.

DITHER=mode

selects the specific type of dithering to use color quantization; mode can be

FS -- Floyd-Steinberg dithering
ORDERED -- ordered dithering
NONE -- no dithering.

PBM

FORMAT=PBM

PCD

FORMAT=PCD

specifies photo CD format. FORMAT=PCD RES= specifies the image resolution to be read. Photo CD images have multiple resolution images in each image. Values are:

BASE/64	64x96
BASE/16	128x192
BASE/4	256x384
BASE	512x768 (default)
4BASE	1024x1536
16BASE	2048x3072.

PCX

FORMAT=PCX

is not supported for writing.

PNG

FORMAT=PNG

TGA

FORMAT=TGA

TIFF

FORMAT=TIFF

XBM

FORMAT=XBM

XPM

FORMAT=XPM

is supported only under the X Windows System under UNIX.

XWD

FORMAT=XWD

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