# IBM Visualization Data Explorer User's Reference

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### 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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