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The image yourself and displaying it with TV will give you greater control. The TVSCL procedure provides a quick way to display an image so that you will get good contrast. Will look the same as that displayed with those above. The image displayed with the following commands You can accomplish the same rescaling by using the TVSCL procedure. ScImage is a new array of the same size as image but with a range of values from 0 to !D.N_Colors. IDL> scImage=BytScl(image,TOP=!D.N_Colors-1) The color table by use of the BytScl function. Range of colors in the color table is stored in the system variable !D.N_Colors. The image that is displayed may not look like what you expect because the range of values may not match theĬolor table or because the image color table was different than the current color table. IDL> Window,/FREE,XSIZE=imSize,YSIZE=imSize An example of the use of Size is: IDL> imSize=SIZE(image) However, you will often want to automate the process so you can put it into a program. Help command and then typing the parameters into the Window You could do this manually by finding the size with the Out the size of the image and open a window to match it. If you want to put the image into a window of the same size, then you need to find If there is no open window, then one with the default Then the image will be displayed in the current window. Other parameters are available, as described in IDL Help. If they are used, they determine the offset of the image origin from These procedures use the same argumentsĪnd keywords and differ only in that TVSCL scales the image into the intensity range of the display device, while IDL uses two commands to display image data on the screen: TV and TVSCL. You can control the position of a window on the screen by using the XPOS and YPOS keyword parameters. If the window is open, then this command also erases the contents. If you want to open or resize a window with a particular window index n then use the command IDL> WINDOW,n,XSIZE=imSize,YSIZE=imSize IDL> WINDOW,/FREE,XSIZE=imSize,YSIZE=imSize Window that it fits with the following commands: IDL> imSize=SIZE(image) Images that are read with the READ_GIF procedure are two dimensional. Of the right size, you have to find out the size of the image and then open a window of that size. However, the result may be a window of the wrong size or location on the screen. Will display an image in the active window or open a new window if there is no active window. The image display procedures, TV and TVSCL that are discussed below The Query_xxx functions are particularly useful in cases where you want to avoid trying There is a Query_Gif function, and a similar function for each imageįormat that IDL understands. Image file by using a Query_xxx function.
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Sometimes you want information about an image before attempting to read it. The Read_Gif command, for example, lets you load the color table into three color variables. If an image file contains a color table for that image, then it makes sense to use it when displaying the image
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The Read_GifĬommand can read the color table from the image.gif file if it exists. It will use the current IDL color table, so it may not look exactly like the original image. The image can now be displayed as describedīelow.
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In this example, image is a byte array with 716 columns and 567 rows. You can get information by using the Help The array image will now be an array of bytes. You can do theįollowing: IDL> fname=Dialog_Pickfile(FILTER='*.gif')
#Loadct idl full
The added advantage that it will construct a full file name for whatever machine is being used. I find it handy to use the Dialog_Pickfile function to help me pick the full name of the image file. For simplicity, we will discuss only the Read_Gif procedure. Each procedure has keyword parameters to set. The supported formats in IDL version 5.2 include: BMP, DICOM, GIF, JPEG, PICT, PNG, PPM, SRF, Look in the IDL Help index forįurther information. IDL provides routines of the form Read_xxx to read a number of image formats. Named image by executing the command IDL> Read_Gif,'C:\myimages\scene.gif',image If the directory is named myimages on the C drive then you could read the image into an array In a directory then you can read it by supplying the path to the image to the Read_Gif For example, if you have an image named scene.gif Image data can be read from files in several formats. Reading information from image displays.We will enlarge this toolbox as we go along in the course. To get you started with a basic set of tools. IDL provides many tools for displaying, modifying and analyzing images.