Legacy Document

Inside Macintosh: Imaging With QuickDraw /

Chapter 6 - Offscreen Graphics Worlds / Offscreen Graphics Worlds Reference

Routines

Managing an Offscreen Graphics World's Pixel Image

Use the GetGWorldPixMap function to obtain a handle to the PixMap record for an offscreen graphics world. You can then pass this handle, which is of data type PixMapHandle, in parameters to several routines that allow you to manage an offscreen graphics world's pixel image.

To prevent the base address for an offscreen pixel image from being moved (while you draw into or copy from its pixel map, for example), pass its handle to the LockPixels function. When you are finished drawing into or copying from an offscreen pixel map, pass its handle to the UnlockPixels procedure.

You can use the AllowPurgePixels procedure to make the base address for an offscreen pixel image purgeable. To prevent the Memory Manager from purging the base address for an offscreen pixel map, use the NoPurgePixels procedure.

To save the current information about the memory allocated for an offscreen pixel image, you can use the GetPixelsState function. To restore this state, you can use the SetPixelsState procedure.

You can use the GetPixBaseAddr function to obtain a pointer to the beginning of a pixel image in memory. You can use the PixMap32Bit function to determine whether a pixel map requires 32-bit addressing mode for access to its pixel image.

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Subtopics

GetGWorldPixMap

LockPixels

UnlockPixels

AllowPurgePixels

NoPurgePixels

GetPixelsState

SetPixelsState

GetPixBaseAddr

PixMap32Bit