The ImageDescription QuickTime structure contains informations that describe the characteristics of a compressed image or sequence.
The QTPlgImageDesc class provides you with properties and methods that let you whether access or create new instances of such a QuickTime description structure. Also, you can use instances of this class as a convenient container for image settings that you will use in any way you like it. Many of the QTPlugin classes make use of this class to allow you to get or set the appropriate image parameters.
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The QTPlgImageDesc class constructors are called when you create a new instance of the class, while the ˜QTPlgImageDesc class destructor, is called automatically when the class is no more in use. Also, you can invoke the class destructor by setting the instance of the class to nil.
Once a new class instance is returned, it is good practice to check the class property to be sure that the new object can be used. See the validity requirements for more details.
The class provides you with the following initializer methods:
()
This is the default constructor. Use this constructor to create a completely new data descriptor container in memory.
All of the class properties are intialized to 0
(other as QTPlgImageDesc)
This is the copy constructor. The properties of the object to be copied will be used to initialize the
new class instance properties
returns the handle to the image description structure in use.
useful for toolbox programmers (use with care: you could invalidate the handle causing unpredictable results
(probably an application crash))
indicates the 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 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
indicates the degree of spatial compression performed on the image data associated with this description.
This property is valid for sequences and still images. You can use values ranging within the quality interval defined by the
listed in
the plugin module
indicates the degree of temporal compression performed on the image data associated with this description.
This property is valid only for sequences. You can use values ranging within the quality interval defined by the
listed in
the plugin module
specifies the width of the source image, in pixels
specifies the height of the source image, in pixels
specifies the width and height, in pixels, of the source image
specifies the width, in pixels, of the encoded image. Usually, but not always, this is
the 's property value
requires QuickTime 7.0 or later.
[Deprecated]: since version 6.6 of the plugin this property is deprecated and will be removed in a future version of the plugin; use the class property instead
[Deprecated]: since version 6.6 of the plugin this property is deprecated and will be removed in a future version of the plugin; use the class property instead
specifies the height, in pixels, of the encoded image. Usually, but not always, this is
the 's property value
requires QuickTime 7.0 or later.
[Deprecated]: since version 6.6 of the plugin this property is deprecated and will be removed in a future version of the plugin; use the class property instead
[Deprecated]: since version 6.6 of the plugin this property is deprecated and will be removed in a future version of the plugin; use the class property instead
specifies if the video is interlaced. If this property is false, then the video is progressive scan
contains the number of frames in the image data associated with this image description structure
contains the horizontal resolution of the source image, in dots per inch
contains the vertical resolution of the source image, in dots per inch
indicates the size of the compressed image, in bytes.
Set this property to 0 if the size is unknown
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
specifies the gamma level described by the image description. To remove this information from the image description object simply set this property to
0
specifies a portion of the image to compress. The specified rectangle must be contained within the rectangle specified by the
and
properties of the class
indicates the 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 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
indicates the compression algorithm used to create the compressed data. This property is stored in string that
always takes up 32 bytes no matter how long the string is. The value of this property should
correspond to the compressor type specified by the codec property. This value is always stored in MacRoman encoding
this property allows you to retrieve detailed information about the selected codec
describes the clean aperture of the buffer. If not specified explicitly in the image description in use, the default clean aperture
(full encoded and
) will be returned
describes the .
If not specified explicitly in the image description, a square (1:1)
pixel aspect ratio will be returned
specifies the values of the dimensions of the different
.
The
property indicates the width and height suitable for using when creating a
to hold this image data
requires QuickTime 7.0 or later
specifies the width and height, in pixels, of the encoded image. Usually, but not always, these values are the same as the values of the
class property. This property is intended to replace the
and
class properties
requires QuickTime 7.0 or later
specifies additional color information. Note that, if you have specified a value for the image description in use, you should
set this property as well with valid video color informations
a localized, human readable string summarizing the image as a string. The elements are:
- the
- the
- parenthetically the clean aperture mode dimensions, but only if they are different from the encoded pixels dimensions
- the
requires QuickTime 7.0 or later
[Removed]: since version 6.5 of the plugin these constants have been removed; use the
of the plugin
module instead