idSize

Defines the total size of this image description structure with extra data including color lookup tables and other per sequence data.

cType

Indicates the type of compressor component that created this compressed image data. The value of this field indicates the compression algorithm supported by the component. The Codec data type defines a field in the compressor name list structure that identifies the compression method employed by a given compressor component. Apple Computer's Developer Technical Support group assigns these values so that they remain unique. These values correspond, in turn, to text strings that can identify the compression method to the user. See the description of GetCodecNameList for a list of valid values.

resvd1

Reserved for Apple. This field must be set to 0.

resvd2

Reserved for Apple. This field must be set to 0.

dataRefIndex

Reserved for Apple. This field must be set to 0.

version

Indicates the version of the compressed data. The contents of this field should indicate the version of the compression algorithm that was used to create the compressed data. By examining this field, decompressors that support many versions of an algorithm can determine the proper way to decompress the image.

revisionLevel

Indicates the version of the compressor that created the compressed image. Developers of compressors and decompressors assign these version numbers.

vendor

Identifies the developer of the compressor that created the compressed image.

temporalQuality

Indicates the degree of temporal compression performed on the image data associated with this description. This field is valid only for sequences.

spatialQuality

Indicates the degree of spatial compression performed on the image data associated with this description. This field is valid for sequences and still images.

width

Contains the width of the source image, in pixels.

height

Contains the height of the source image, in pixels.

hRes

Contains the horizontal resolution of the source image, in dots per inch.

vRes

Contains the vertical resolution of the source image, in dots per inch.

dataSize

Indicates the size of the compressed image, in bytes. This field is valid only for still images. Set this field to 0 if the size is unknown.

frameCount

Contains the number of frames in the image data associated with this description.

name

Indicates the compression algorithm used to create the compressed data. This algorithm is stored in Pascal string format. It always takes up 32 bytes no matter how long the string is. The 32 bytes consist of 31 bytes plus one length byte. The value of this field should correspond to the compressor type specified by the cType field, as well as to the value of the typeName field in the appropriate compressor name structure returned by the GetCodecNameList function. Applications may use the contents of this field to indicate the type of compression used for the associated image.

depth

Contains the pixel depth specified for the compressed image. Values of 1, 2, 4, 8, 16, 24, and 32 indicate the depth of color images. Values of 34, 36, and 40 indicate 2-bit, 4-bit, and 8-bit grayscale, respectively, for grayscale images.

clutID

Contains the ID of the color table for the compressed image, or other special values. If this field is set to 0, then a custom color table is defined for the compressed image. You can use the GetImageDescriptionCTable function to retrieve the color table. If this field is set to -1, the image does not use a color table.