GetCTable

GetCTable
Header:	Quickdraw.h		Carbon status:	Supported

Obtains a color table stored in a 'clut' resource.

CTabHandle GetCTable (
    SInt16 ctID
);

Parameter descriptions

ctID: The resource ID of a 'clut' resource.

function result: A handle to the color table. If the 'clut' resource with that ID is not found, GetCTable returns NULL.Before you place this handle in the pmTable field of a PixMap structure, first use the DisposeCTable function to dispose of the handle already there.

DISCUSSION

Before you modify a ColorTable structure, change its ctSeed field to invalidate it. To do this, use the CTabChanged function.

The GetCTable function recognizes a number of standard 'clut' resource IDs. You can obtain the default grayscale color table for a given pixel depth by calling GetCTable, adding 32 (decimal) to the pixel depth, and passing these values in the ctID parameter:

A pixel depth of 1

Pass a resource ID of 33. Color table composition: black, white.
A pixel depth of 2

Pass a resource ID of 34. Color table composition: black, 33% gray, 66% gray, white.
A pixel depth of 3

Pass a resource ID of 35. Color table composition: black, 14 shades of gray, white.
A pixel depth of 4

Pass a resource ID of 36. Color table composition: black, 254 shades of gray, white.

For full color, obtain the default color tables by adding 64 to the pixel depth and passing these values in the ctID parameter:

A pixel depth of 2

Pass a resource ID of 66. Color table composition: black, 50% gray, highlight color, white.
A pixel depth of 4

Pass a resource ID of 68. Color table composition: black, 14 colors including the highlight color, white.
A pixel depth of 8

Pass a resource ID of 72. Color table composition: black, 254 colors including the highlight color, white.

SPECIAL CONSIDERATIONS

The GetCTable function may move or purge memory blocks in the application heap; do not call this function at interrupt time.

AVAILABILITY

Supported in Carbon. Available in Carbon 1.0.2 and later when running Mac OS 8.1 or later.