IBM Visualization Data Explorer User's Reference

ReadImage

Category

Import and Export

Function

Reads an image from an image file.

Syntax

image = ReadImage(name, format, start, end, delta, width, height);

Inputs

Name	Type	Default	Description
name	string	"image"	file name
format	string	"rgb" or input dependent	file format
start	integer	first frame	first movie frame
end	integer	last frame	last movie frame
delta	integer	1	delta of images to be read
width	integer	input dependent	width of image
height	integer	input dependent	height of image
delayed	flag	environment dependent	use delayed colors if present in file
colortype	string	environment dependent	data type for colors

Outputs

Name	Type	Description
image	image or image series	resulting image

Functional Details

This module supports four basic file formats: RGB and TIFF (Tag Image File Format), GIF (Graphics Interchange Format), and MIFF.

name	is the name of the image file. If name contains a series, the parameters start, end, and delta can be used to read a subset of the images (see parameter descriptions).
format	specifies the format of the image file. This parameter is not required if name includes a file extension defining the format (see following table). If name is specified without the appropriate extension, then the file format must be specified. If format is specified as "rgb," and name is "image," the module will first try to open image.rgb. If that fails, it will then try to open image. File Type Format Specifier Expected File Extension(s) Multiframe/Series Data RGB "rgb" "r+g+b" .rgb and .size .r, .g, .b, .size, Yes TIFF "tiff" .tiff Yes GIF "gif" .gif No MIFF "miff" .miff Yes
start  and  end	specify the first and last frame to be read from an image file containing a series.
delta	specifies the increment in counting the frames in the range from start to end. For example, if the first and last frames are 10 and 20 respectively, and delta = 2, the output (image) is a series group with six members (indexed from 0 to 5). Frame numbers (10, 12,..., 20 in this example) are preserved as the series position number.
width  and  height	are used only for RGB format files. The module obtains information about the size and number of images from name.size, an ASCII file containing the string "w×h×f," (where w and h are pixel width and height of image respectively, and f is the number of frames). If the .size file is not available, then width and height can be used to specify the size of the image(s).
delayed	specifies whether ReadImage should create a "delayed color" image if the image file is stored in an "image with colormap" format. By default, ReadImage will create a "delayed color" image if possible, unless the environment variable DXDELAYEDCOLORS is set to 0, or the delayed parameter is set to 0.
colortype	specifies whether the colors in the image should be byte or floating point. By default, ReadImage will create byte colors unless the DXPIXELTYPE environment variable is set to DXFloat, or colortype is set to "float".

Notes:

1. RGB format files can be either "rgb" or "r+g+b." The file format "rgb" contains the image with the bytes for the red, green, and blue values interleaved. An alternate file format is "r+g+b," where three output files contain the non-interleaved image: "name.r," "name.g," and "name.b."

   TIFF format files must be either full color RGB images (TIFF Class R) or palette color RGB images (TIFF Class P), uncompressed ("Compression=1"), and interleaved ("PlanarConfiguration=1"). If the extension is not part of the name, the format must be set to "tiff." Information about the size of the image is obtained from the file itself, since TIFF files are self-describing. (For more information on file formats, see WriteImage.)

2. The default behavior of ReadImage is different in Data Explorer version 3.1.4 and above in terms of the type of image it creates internally. If you do not specify the environment variable DXPIXELTYPE as "DXFloat", ReadImage will create byte colors internally. This will result in reduced storage required for the image, and will only affect networks that require the colors to be of type float, in which case the ReadImage parameter "colortype" should be set to "float", or the DXPIXELTYPE environment variable should be set to "DXFloat".

3. ReadImage will also maintain the delayed color status of an image, as will be the case for GIF, some TIFF, and some MIFF format files. If the visualization program requires full colors for each pixel, set the ReadImage "delayed" parameter to false (0) or set the environment variable DXDELAYEDCOLORS to 0.

4. If you want to convert an image file that does not already have delayed colors to one that does, use ReadImage to load it in and then use QuantizeImage to make it delayed color.

Components

Creates an output with "positions," "connections," and "colors" components.

Example Visual Programs

ReadImage.net
UsingFilter.net

See Also

 WriteImage

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