IMAGE_CREATE Function

Creates an image associative array. Refer to IMAGE_READ Function for a list of supported file types.

Usage

image = IMAGE_CREATE(pixel_array)

Input Parameters

pixel_array—An array containing image data. The input array must be in one of the following forms, where w is the image width, h is the height, and img_count, an optional parameter, is the number of images in the array:

• (w, h[, img_count])—8-bit (pseudo-color) images

• (3, w, h[, img_count])—24-bit (RGB) images, pixel interleaved

• (w, 3, h[, img_count])—24-bit (RGB) images, row interleaved

• (w, h, 3[, img_count])—24-bit (RGB) images, image interleaved

Returned Value

image—An image associative array.

Keywords

Colormap—A 3-by-n colormap array.

Colormodel—A long integer specifying the color model:

• 0—Monochrome or gray scale

• 1—RGB

• 2—CMY (Currently not supported)

• 3—HSV (Currently not supported)

Comments—A string containing additional information about the image. This feature is supported for GIF,  JPEG,  MIFF,  PNG,  TGA,  and TIFF formats.

Depth—A long integer specifying the number of bits per channel. (Default: 8)

File_Name—A string containing a default filename for the image.

File_Type—A string specifying the type of image file to create. For example, 'sun' denotes a Sun Rasterfile. (Default: TIFF)

Getcolormap—When specified IMAGE_CREATE uses the current colormap.

Img_Count—A long integer specifying the number of images in the output array image. (Default: 1)

Intleave—A scalar STRING indicating the interleaving of the pixel array when it cannot be determined by examining the pixel array itself.

PV‑WAVE attempts to determine the interleaving of the pixel array by locating the smallest dimension. In cases where this is ambiguous, for example the pixel data has multiple dimensions of size '3' or the height and/or width of the image is less than '3', PV‑WAVE may fail to create the image. In these cases, use the Intleave keyword to indicate to PV-WAVE what the interleaving of your pixel array is.

Valid strings and the corresponding interleaving methods are:

'image'—The RGB pixel array arrangement is (x, y, 3) for 3 image-interleaved channels of x-by-y pixels.

'row'—The RGB pixel array arrangement is (x, 3, y) for 3 row-interleaved channels of x-by-y pixels.

'pixel'—The RGB pixel array arrangement is (3, x, y) for 3 pixel-interleaved channels of x-by-y pixels.

Quiet—Suppresses successive levels of error messages, depending on the value set. This keyword accepts the same integer values used with the system variable !Quiet.

Units—Units of pixel size. (1 = inches; 2 = millimeters)

X_resolution—Pixel size in Units.

Y_resolution—Pixel size in Units.

Discussion

The IMAGE_CREATE function creates an image associative array. Complete image information is stored in this type of array, which is used by all of the IMAGE_* routines in PV‑WAVE. (Refer to the PV‑WAVE Programmer’s Guide for additional information on associative arrays.)

The image associative array allows the following operations:

• File I/O of images to and from different file formats

• Displaying images

• Processing images

Image Associative Array Structure

Image Associative Array’s Keys describes each key of the image associative array.

Image Associative Array’s Keys

Array Key Name	Variable Type	Description
file_name	STRING	Absolute or relative pathname of an image file
file_type	STRING	The type of image file. (See IMAGE_READ for a list of supported file types.)
width	LONG	Image width
height	LONG	Image height
img_num	LONG	Index number in the range {0...n} of a subimage in the file (if the image was created with IMAGE_READ)
img_count	LONG	Number of subimages in the pixel array
PIXELS:
nr_cc	LONG	Number of color channels. This item specifies how many storage units are allocated per pixel. (Supported values: 1 and 3)
depth	LONG	Bits per color channel
pixel_dtype	LONG	Data type of the pixel array:   1 = BYTE   2 = INT **  3 = LONG **13 = INT32**
interleave	LONG	Interleave method used:   1 =  Pixel interleaving   2 =  Row interleaving   3 =  Image interleaving
color_model	LONG	Color model:   0 = Monochrome or gray scale  1 = RGB  2 = CMY (currently not supported)   3 = HSV (currently not supported)
pixels	BYTE INT ** LONG ** INT32 **	A multidimensional array describing an 8-bit or 24-bit image. Refer to the Pixel Arrays section later for a description of supported pixel arrays.
x_resolution	FLOAT	Pixel size in units
y_resolution	FLOAT	Pixel size in units
units	LONG	Units of pixel size:    1 = (inches)    2 = (mm)
COLORMAP:
cmap_type	LONG	Type of colormap:    0 = No colormap   1 = 1 colormap vector (not supported)   2 = Multiple colormap vectors
cmap_dtype	LONG	Data type of colormap (only BYTE (1) is supported)
n_colors	LONG	Number of entries in the colormap
colormap	BYTE INT ** LONG ** INT32 **	Array whose dimensions depend on cmap_type and n_colors. cmap_type:    1 = not supported    2 = (3 , n_colors)
SUPPLEMENTARY and CONTROL:
label	STRING	Optional annotation (Note: None of the supported graphics file types currently support labels.)
comments	STRING	Optional information about source, etc.
status	LONG	0 = success; < 0 = error
** This data type is currently not supported for IMAGE_READ and IMAGE_WRITE. IMAGE_CREATE accepts an array in this data type, but before writing the image to a file the pixel array must be converted to BYTE.

Pixel Arrays

Valid Pixel Arrays describes valid pixel arrays.

Valid Pixel Arrays

Color Model	Color Channels, Number(nr_cc)	Bits per pixel	Colormap	Color Channels in Colormap, Number	Dimensions, pixel array
RGB	3	24	Optional	3, if colormap present
GrayScale	1	8	Yes	3	2D **
Pseudo Color	1	8	Yes	3	2D **
** Refer to the Pixel Array Dimensions table for more information.

Pixel Array Dimensions

Pixel Array Dimensions describes the valid pixel array dimensions. The dimensions of the pixel array (width, height, nr_images, etc.) refer to keys in the image associative array.

Pixel Array Dimensions

Type of Array	Description
2D Pixel Arrays:
(width, height[, nr_images])	8-bit (pseudo-color) image
3D Pixel Arrays:
(nr_cc, width, height[, img_count])	24-bit (RGB) image, pixel interleaved
(width, nr_cc, height[, img_count])	24-bit (RGB) image, row interleaved
(width, height, nr_cc[, img_count])	24-bit (RGB) image, image interleaved

Example 1

This example demonstrates how IMAGE_CREATE creates an image associative array. The associative array is listed using the INFO command.

; Create some pixel data (all zeros).
pixels = BYTARR(100, 200)

; Create a colormap (all zeros).
cmap = BYTARR(3, 50)
; Create the image associative array. Next, use 
; INFO to display the contents of the array.
image = IMAGE_CREATE(pixels, File_name='test.tif', $
   Colormap=cmap, File_type='tif') 
INFO, image, /Full

IMAGE	AS. ARR	=	Associative Array(22)
label	STRING	=	''
file_type	STRING	=	'tif'
height	LONG	=	200
units	LONG	=	2
img_num	LONG	=	0
y_resolution	FLOAT	=	72.0000
pixels	BYTE	=	Array(100, 200)
color_model	LONG	=	1
n_colors	LONG	=	50
file_name	STRING	=	'test.tif'
width	LONG	=	100
cmap_type	LONG	=	2
x_resolution	FLOAT	=	72.0000
status	LONG	=	0
img_count	LONG	=	1
nr_cc	LONG	=	1
depth	LONG	=	8
colormap	BYTE	=	Array(3, 50)
cmap_dtype	LONG	=	1
comments	STRING	=	' '
pixel_dtype	LONG	=	1
interleave	LONG	=	3

Example 2

; Make up some unsigned 16-bit data and put it in a long array.
img = IMAGE_READ(!Dir + '/demo/gallery3/data/veggies.jpg')
img = SCL(img('pixels'), 65535, /Long)
WINDOW, Xsize=800
TVSCL, img

; Write a 16-bit tiff file.
status = IMAGE_WRITE('image_create_ex2.tif', $
   IMAGE_CREATE(img, Comments='little', Depth=16))

; Read it back in.
new_img = IMAGE_READ('image_create_ex2.tif', File_type='tiff16')

INFO, new_img, /Full
TVSCL, new_img('pixels'), 400, 0

See Also

IMAGE_DISPLAY,   IMAGE_READ,  IMAGE_WRITE

System Variables:  !Quiet