SAS Component Language: Reference

Attributes for Reading Image Files

Reader Attributes for Supported File Types 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.

Reader Attributes for Supported File Types
File Type Reader Attributes Comment

BMP FORMAT=BMP

COMPRESS=NONE Default.

COMPRESS=RLE Run-length encoded data.

CAT FORMAT=CAT

DIB FORMAT=DIB Supported only under the Windows 95, Windows 98, Windows NT, and OS/2 operating systems.

EMF FORMAT=EMF Supported only under Windows 95, Windows 98, and Windows NT.

EPSI FORMAT=EPSI

DPI=num
Number of dots per inch specified when the output file was created.

GIF FORMAT=GIF

JFIF FORMAT=JFIF Required for reading JPEG files that use the JPEG File Interchange Format (JFIF).

DCT=mode Specifies which 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 much slower unless the host has very fast floating-point hardware.

The results of the floating-point method can vary across host machines, whereas the integer methods should give the same results on all hosts.

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 Writes to the SAS log the version number and copyright messages for the Independent JPEG Group's JFIF software.

FAST Enables certain recommended processing options for fast, low quality output. Specifying FAST is 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 requires 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 between 2 and 256, inclusive.

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 you are processing a large image and only a smaller version is needed, because the reader is much faster when the output is scaled down.

DITHER=mode
Specifies which type of dithering to use for color quantization. Mode can be

FS Floyd-Steinberg dithering

ORDERED ordered dithering

NONE no dithering.

MET FORMAT=MET Supported only under OS/2.

PBM FORMAT=PBM

PCD 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

PICT FORMAT=PICT Supported only in the Macintosh environment.

PNG FORMAT=PNG

TGA FORMAT=TGA

TIFF FORMAT=TIFF

WMF FORMAT=WMF Supported only under MicroSoft Windows operating systems.

XBM FORMAT=XBM

XPM FORMAT=XPM Supported only by the X Window System under UNIX.

XWD FORMAT=XWD

***Reader Attributes for Supported File Types***
File Type	Reader Attributes	Comment
BMP	FORMAT=BMP
	COMPRESS=NONE	Default.
	COMPRESS=RLE	Run-length encoded data.
CAT	FORMAT=CAT
DIB	FORMAT=DIB	Supported only under the Windows 95, Windows 98, Windows NT, and OS/2 operating systems.
EMF	FORMAT=EMF	Supported only under Windows 95, Windows 98, and Windows NT.
EPSI	FORMAT=EPSI
	DPI=num	Number of dots per inch specified when the output file was created.
GIF	FORMAT=GIF
JFIF	FORMAT=JFIF	Required for reading JPEG files that use the JPEG File Interchange Format (JFIF).
	DCT=mode	Specifies which 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 much slower unless the host has very fast floating-point hardware.
		The results of the floating-point method can vary across host machines, whereas the integer methods should give the same results on all hosts.
	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	Writes to the SAS log the version number and copyright messages for the Independent JPEG Group's JFIF software.
	FAST	Enables certain recommended processing options for fast, low quality output. Specifying FAST is 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 requires 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 between 2 and 256, inclusive.
	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 you are processing a large image and only a smaller version is needed, because the reader is much faster when the output is scaled down.
	DITHER=mode	Specifies which type of dithering to use for color quantization. Mode can be
		FS	Floyd-Steinberg dithering
		ORDERED	ordered dithering
		NONE	no dithering.
MET	FORMAT=MET	Supported only under OS/2.
PBM	FORMAT=PBM
PCD	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
PICT	FORMAT=PICT	Supported only in the Macintosh environment.
PNG	FORMAT=PNG
TGA	FORMAT=TGA
TIFF	FORMAT=TIFF
WMF	FORMAT=WMF	Supported only under MicroSoft Windows operating systems.
XBM	FORMAT=XBM
XPM	FORMAT=XPM	Supported only by the X Window System under UNIX.
XWD	FORMAT=XWD

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