Inside Macintosh: Imaging with QuickDraw
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QuickDraw automatically creates pixel maps when you create a color window with the GetNewCWindow or NewCWindow function (described in the chapter "Window Manager" in Inside Macintosh: Macintosh Toolbox Essentials ), when you create offscreen graphics worlds with the NewGWorld function (described in the chapter "Offscreen Graphics Worlds" in this book), and when you use the OpenCPort function. QuickDraw also disposes of a pixel map when it disposes of a color graphics port. Although your application typically won't need to create or dispose of pixel maps, you can use the NewPixMap function and the CopyPixMap procedure to create them, and you can use the DisposePixMap procedure to dispose of them. Although you should never need to do so, you can also set the pixel map for the current color graphics port by using the SetPortPix procedure.
Although you typically don't need to call this routine in your application code, you can use the NewPixMap function to create a new, initialized PixMap record.
FUNCTION NewPixMap: PixMapHandle;
The NewPixMap function creates a new, initialized PixMap record and returns a handle to it. All fields of the PixMap record are copied from the current device's PixMap record except the color table. In System 7, the hRes and vRes fields are set to 72 dpi, no matter what values the current device's PixMap record contains. A handle to the color table is allocated but not initialized.
You typically don't need to call this routine. PixMap records are created for you when you create a window using the Window Manager functions NewCWindow and GetNewCWindow and when you create an offscreen graphics world with the NewGWorld function.
If your application creates a pixel map, your application must initialize the PixMap record's color table to describe the pixels. You can use the GetCTable function (described on GetCTable ) to read such a table from a resource file; you can then use the DisposeCTable procedure (described on DisposeCTable ) to dispose of the PixMap record's color table and replace it with the one returned by GetCTable .
Although you typically don't need to call this routine in your application code, you can use the CopyPixMap procedure to duplicate a PixMap record.
PROCEDURE CopyPixMap (srcPM,dstPM: PixMapHandle);
The CopyPixMap procedure copies the contents of the source PixMap record to the destination PixMap record. The contents of the color table are copied, so the destination PixMap has its own copy of the color table. Because the baseAddr field of the PixMap record is a pointer, the pointer, but not the image itself, is copied.
Although you should never need to do so, you can set the pixel map for the current color graphics port by using the SetPortPix procedure.
PROCEDURE SetPortPix (pm: PixMapHandle);
The SetPortPix procedure replaces the portPixMap field of the current CGrafPort record with the handle you specify in the pm parameter.
The SetPortPix procedure is analogous to the basic QuickDraw procedure SetPortBits , which sets the bitmap for the current basic graphics port. The SetPortPix procedure has no effect when used with a basic graphics port. Similarly, SetPortBits has no effect when used with a color graphics port.
Both SetPortPix and SetPortBits allow you to perform drawing and calculations on a buffer other than the screen. However, instead of using these procedures, you should use the offscreen graphics capabilities described in the chapter "Offscreen Graphics Worlds."
Although you typically don't need to call this routine in your application code, you can use the DisposePixMap procedure to dispose of a PixMap record. The DisposePixMap procedure is also available as the DisposPixMap procedure.
PROCEDURE DisposePixMap (pm: PixMapHandle);