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9 READING AND DISPLAYING IMAGE FILES

The term "IUE image files" is used to refer to raw image files, the photometrically-corrected files, and the line-by-line files. The programs to read these files generally return a two-dimensional array (IMAGE), and they all expect the name of the data file to be entered in quotes ('IMAGET'). Although the programs to read the line-by-line files have already been discussed in the previous chapter, the display routines RDZ and READFILE described below pertain to all the above file types.

For reading NEWSIPS RILO/RIHI files, you may use READRI. The IMAGE parameter will be a byte array containing the data (the units will be ``data numbers'' or DNs). Note that some partial read RILO files may have an image extension containing the unshifted raw image data. Although probably of little use to users, the exhd and eximage parameters in READMX can be used to extract this data.

READRI,'IMAGET',H,IMAGE,exhd,eximage

READLI,'IMAGET',H,IMAGE,Q

For LILO/LIHI files, use READLI. The IMAGE parameter will be a 768 × 768 integer array containing the data (the units will be ``flux numbers'' or FNs) and the Q parameter will contain `` $\nu$ '' quality flags for each datum.

The RDAF-format IUESIPS raw and PI data may both be read using the program READFILE:

READFILE,'IMAGET',LAB,IMAGE,isize

IMAGET Raw, PI, or FES file to read (IUESIPS only).
LAB VICAR label, returned as an ASCII string array.
IMAGE Two-dimensional image array of fluxes.
isize If you wish to read only a section of an image file, you may enter the starting line and sample numbers, and the number of lines and samples to read, as a four element vector via this keyword (e.g., isize=[24,1,8,2048] means read 8 lines starting with line 24, and 2048 samples starting with sample 1). NOTE: Sample refer to bytes and not data points!

Note that the PI and LI files are large, and may cause memory problems if you try to read the whole image. It is recommended that you use the ISIZE keyword and read sections of the image if you encounter memory problems.

The Data Analysis Center does not have software to extract spectra from these image files. You may display them on a workstation or image display device (if you have one) using RDZ or IUEDISPLAY. Both programs will display a scaled byte version of the input image in a window of the approriate size.

RDZ is useful when you want to display an array that you have already stored in memory (e.g., after running READFILE, READSI, etc.), or if you want to display flux values and (for line-by-line files) wavelengths. Coordinates of the crosshairs (controlled by a mouse) are continuously displayed. You may click the left mouse button to zoom, the middle mouse button to restore the original image, and the right mouse button to exit the program.

RDZ,IMAGE,w,ifact,/noscale,/nodelete,resize=sfact,olay=m

IMAGE This is the input two-dimensional array of (uncalibrated) fluxes.
w For line-by-line images, you may have a wavelength array. If you enter a wavelength array, the current wavelength will be displayed along with the row and column numbers. See instructions on reading the LBL files as images. For NEWSIPS SIHI files, w should be a 2-dimensional array of 5 x m points (where m is the number of orders) as generated by the program READSI. The 5 columns represent starting wavelength, wavelength increment, order number, found line position of spectrum centroid, and slit height for each order.
ifact Integer zoom factor (default is 4).
noscale Normally, zoomed images are rescaled to the range 0 through 255 before displaying. Use this keyword if you want the color mapping to remain the same as in the original full-size image.
nodelete Normally, the window containing the image is destroyed when you exit RDZ. If you wish to leave it on the screen, you may set this keyword.
resize Optional keyword to reduce or increase the size of the input image by a factor of sfact. Sfact must be an integer or integer fraction. To reduce image by a facter or 2 for example, set resize = 0.5. (Useful when the displayed image normally covers the screen). To increase the image size , set resize = 2.
olay For SIHI images only, this keyword will overlay the position of the gross flux extraction slit for the specified orders. For example, to see the extraction region for orders 100 and 110, enter: olay=[100,110].

RDZ assumes you have already read the data into memory. To display an image directly from the disk file, you may use IUEDISPLAY:

IUEDISPLAY,'IMAGET',image,/cbar,ctab=ctab

IMAGET Image file to read.
image Two dimensional array of fluxes, if the user wishes to have them returned on exiting IUEDISPLAY.
cbar If this keyword is set, a color bar (about 2% of the image size) will be included in the image showing the color mapping for
ctab Color table to use: 'IUE' (similar to the color table one would see in the Telescope Operations Center display), a number from 100 through 115 (original color tables from Dave Stern), or a number from 200 through 215 (additional color tables from the Ultraviolet Imaging Telescope project). For X or Mac devices, the default is to not change the current color table.

The IDL procedure XLOADCT is available if you wish to change the color table on workstations. This is a ``widget'' procedure that brings up a window with slider bars for changing contrasts, and a list of color tables you can click on. Type XLOADCT to use it. You can use the IUEDAC procedure IUELCT whether you are using a workstation or an IVAS. This procedure prints a list of color tables and prompts you to enter the number corresponding to the one you want, if you call it without any parameters: IUELCT.

For users who want to make hardcopies of their image files, or who want to create a quick postscript image file, there is a program called WDUMP. WDUMP is a general routine for dumping the contents of the current plotting window to a postscript file.

WDUMP,DUMMY,print=print,color=color,maxsize=maxsize

DUMMY A dummy parameter to allow the calling sequence to be displayed.
PRINT Print command if it differs from that in !iueprint.com. Required if !iueprint.type does not equal 'ps'. If the color keyword is set, this keyword will be ignored.
COLOR If present then the file created is a color postscript file.
MAXSIZE Determines maximum dimension of color postscript image in inches. Default = 8.0 inches. Keyword is ignored if /COLOR is not specified.

Next: 10 MORE WAYS TO Up: IUE DATA ANALYSIS CENTER Previous: 8.6 High Dispersion Extraction

2/9/1998

IMAGET	Raw, PI, or FES file to read (IUESIPS only).
LAB	VICAR label, returned as an ASCII string array.
IMAGE	Two-dimensional image array of fluxes.
isize	If you wish to read only a section of an image file, you may enter the starting line and sample numbers, and the number of lines and samples to read, as a four element vector via this keyword (e.g., isize=[24,1,8,2048] means read 8 lines starting with line 24, and 2048 samples starting with sample 1). NOTE: Sample refer to bytes and not data points!

IMAGE	This is the input two-dimensional array of (uncalibrated) fluxes.
w	For line-by-line images, you may have a wavelength array. If you enter a wavelength array, the current wavelength will be displayed along with the row and column numbers. See instructions on reading the LBL files as images. For NEWSIPS SIHI files, w should be a 2-dimensional array of 5 x m points (where m is the number of orders) as generated by the program READSI. The 5 columns represent starting wavelength, wavelength increment, order number, found line position of spectrum centroid, and slit height for each order.
ifact	Integer zoom factor (default is 4).
noscale	Normally, zoomed images are rescaled to the range 0 through 255 before displaying. Use this keyword if you want the color mapping to remain the same as in the original full-size image.
nodelete	Normally, the window containing the image is destroyed when you exit RDZ. If you wish to leave it on the screen, you may set this keyword.
resize	Optional keyword to reduce or increase the size of the input image by a factor of sfact. Sfact must be an integer or integer fraction. To reduce image by a facter or 2 for example, set resize = 0.5. (Useful when the displayed image normally covers the screen). To increase the image size , set resize = 2.
olay	For SIHI images only, this keyword will overlay the position of the gross flux extraction slit for the specified orders. For example, to see the extraction region for orders 100 and 110, enter: olay=[100,110].

IMAGET	Image file to read.
image	Two dimensional array of fluxes, if the user wishes to have them returned on exiting IUEDISPLAY.
cbar	If this keyword is set, a color bar (about 2% of the image size) will be included in the image showing the color mapping for
ctab	Color table to use: 'IUE' (similar to the color table one would see in the Telescope Operations Center display), a number from 100 through 115 (original color tables from Dave Stern), or a number from 200 through 215 (additional color tables from the Ultraviolet Imaging Telescope project). For X or Mac devices, the default is to not change the current color table.

DUMMY	A dummy parameter to allow the calling sequence to be displayed.
PRINT	Print command if it differs from that in !iueprint.com. Required if !iueprint.type does not equal 'ps'. If the color keyword is set, this keyword will be ignored.
COLOR	If present then the file created is a color postscript file.
MAXSIZE	Determines maximum dimension of color postscript image in inches. Default = 8.0 inches. Keyword is ignored if /COLOR is not specified.