Understanding Image Basics
4Understanding Image BasicsIn this chapter . . .[MIPAV_ImageBasics.html#1220264 "Supported graphic formats overview" on page 136][MIPAV_ImageBasics.html#1220316 "Understanding the MIPAV dimensionality and coordinate system" on page 136][MIPAV_ImageBasics.html#1220350 "Data types" on page 138][MIPAV_ImageBasics.html#1220413 "Headers" on page 138][MIPAV_ImageBasics.html#1220437 "Endianness" on page 139][MIPAV_ImageBasics.html#1220445 "Viewing and editing image attributes" on page 139]This chapter also explains the dimensionality and coordinate system used by MIPAV, the data types MIPAV supports, the header offset information, endianness, and how to view and edit image attributes.It also provides a basic information about image file formats supported by MIPAV. More information about graphic file formats and the formats that MIPAV supports can be found in Appendix C: "Supported formats" .
Contents
Supported graphic formats overview
MIPAV supports three categories of graphic file formats: vector (i.e., volume of interest, or VOI), bitmap (i.e., 2D to 5D grayscale or RGB images), and 3D images.Vector file formats are usually used to store line-based elements. These elements can be geometric shapes, such as polygons, curves, or splines. MIPAV can read and generate several vector-formatted file types including the MIPAV lookup table (LUT), MIPAV MTX, MIPAV Graphics Plot (PLT), and MIPAV VOI. See also Appendix C: "Supported formats" on page 561.Bitmap file formats are usually used to store real-world graphics data e.g., photographs or medical images such as CT scans. The data portion of bitmap files contains numerical data that indicates the color of each pixel or voxel in the image. MIPAV can read and generate a number of bitmap formatted file types, such as Adobe Photoshop (PSD), Graphics Interchange File (GIF), Sun Raster (RS), Tagged Image File Format (TIFF), and Truevision Graphics Adapter (TGA).MIPAV uses 3D graphic formatted files to store descriptions of the color and shape of 3D models of real-world and imaginary objects.To support the wide range of image-processing needs of the NIH intramural research community, MIPAV reads and writes the image file types indicated in Table 1, refer to Appendix C: "Supported formats" on page 561.Understanding the MIPAV dimensionality and coordinate system
Internally, MIPAV is designed to store images of any dimensionality and thus is n dimensional. [MIPAV_ImageBasics.html#1220345 Figure 59] is a model of an example 3D-image where each position within the grid represents a voxel.voxel-The smallest distinguishable cube-shaped part of a 3D-image.The voxel in the upper left-most position is considered the origin of the dataset. (A volumetric dataset is a set of cross-sectional images). Ideally, each voxel would be isotropic (i.e., cubic), but clinical datasets are often acquired in such a manner that the resolution in the x and y dimensions is greater than the resolution in the z dimension, thus producing rectangular voxels (elongated in the z direction). This voxel anisotropy is taken into account in the execution of the algorithms found in MIPAV.
Because MIPAV's image storage buffer is n-dimensional, it can store 2D, 3D, and 4D medical images. CT and MRI are examples of 3D medical images where the three dimensions (x, y, and z) are spatial dimensions. Other 3D datasets include fluoroscopy volumes, where the first two dimensions are spatial and the third dimension is time.
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Data types
Data type
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Description
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Boolean
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1 bit per pixel/voxel (1 on, 0 off)
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Signed byte
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1 byte per pixel/voxel (-128, 127)
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Unsigned byte
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1 byte per pixel/voxel (0, 255)
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Signed short
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2 bytes per pixel/voxel (-32768, 32767)
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Unsigned short
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2 bytes per pixel/voxel (0, 65535)
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Integer
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4 bytes per pixel/voxel (-231, 231-1)
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Long
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8 bytes per pixel/voxel (-9.22E18, 9.22E18)
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Float
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4 bytes per pixel/voxel (-3.4E38, 3.4E38)
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Double
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8 bytes per pixel/voxel (-1.8E308, 1.8E308)
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Color 32
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3 bytes per pixel/voxel, plus 1 byte; 8 bits per color channel (alpha, red, green, and blue)
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Headers
Endianness
Viewing and editing image attributes
The Image Attributes window displays the name of the image file and information about the resolution of the image. The About Image window displays more detailed information about the image, such as the orientation of the image or the number of bits per pixel or voxel.
Viewing image attributes
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Editing image attributes
By default, the General page always appears first when the Image Attributes dialog box opens.
Image Attributes dialog box
What's the Difference Between Clicking Apply or Clicking OK? Click Apply when you want the dialog box or window to remain open after it makes the change so that you can make further modifications. If instead you click OK, the dialog box or window closes immediately after making the current change.
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testing section
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