Inside Macintosh: Imaging With QuickDraw /

Appendix A - Picture Opcodes

A Sample Extended Version 2 Picture

The chapter "Pictures" in this book describes how to use the OpenCPicture function to create and display extended version 2 pictures. Listing A-4 illustrates how to use OpenCPicture.

Listing A-4 Creating and drawing an extended version 2 picture

FUNCTION MyCreateAndDrawPict(pFrame: Rect): PicHandle;
VAR
   myOpenCPicParams: OpenCPicParams;
   myPic:            PicHandle;
   trianglePoly:     PolyHandle;
BEGIN
   WITH myOpenCPicParams DO BEGIN
      srcRect := pFrame;
      hRes := gHRes;       {$00480000 for 72 dpi}
      vRes := gVRes;       {$00480000 for 72 dpi}
      version := - 2;      {always set this field to -2}
      reserved1 := 0;      {this field is unused}
      reserved2 := 0;      {this field is unused}
   END;
   myPic := OpenCPicture(myOpenCPicParams);  {start creating the picture}
   ClipRect(pFrame);                      {always set a valid clip region}
   FillRect(pFrame,dkGray);   {create a dark gray rectangle for background}
   FillOval(pFrame,ltGray);   {overlay the rectangle with a light gray oval}
   trianglePoly := OpenPoly;  {start creating a triangle}
   WITH pFrame DO BEGIN
      MoveTo(left,bottom);
      LineTo((right - left) DIV 2,top);
      LineTo(right,bottom);
      LineTo(left,bottom);
   END;
   ClosePoly;                 {finish the triangle}
   PaintPoly(trianglePoly);   {paint the triangle}
   KillPoly(trianglePoly);    {dispose of the memory for the triangle}
   ClosePicture;              {finish the picture}
   DrawPicture(myPic,pFrame);       {draw the picture}
   MyCreateAndDrawPict := myPic;
END;

Figure A-1 shows the picture created by Listing A-4.

Figure A-1 A picture

The QuickDraw drawing commands issued between OpenCPicture and the ClosePicture procedure in Listing A-4 are saved in memory as a Picture record containing a picSize field, a picFrame field, and an array of picture opcodes; an application can also save this information in a resource of type 'PICT'. The DrawPicture procedure reads these opcodes when drawing the picture.

For debugging purposes, you might find it helpful to examine the opcodes for a picture. Listing A-5 shows the extended version 2 picture in Figure A-1 after it is saved in a 'PICT' resource and then decompiled with the DeRez decompiler.

Listing A-5 A decompiled extended version 2 picture

data 'PICT' (128) {
$"0078"     /* picture size; don't use this value for picture size */
$"0000 0000 006C 00A8"  /* bounding rectangle of picture at 72 dpi */
$"0011"     /* VersionOp opcode; always $0011 for extended version 2 */
$"02FF"     /* Version opcode; always $02FF for extended version 2 */
$"0C00"     /* HeaderOp opcode; always $0C00 for extended version 2 */
            /* next 24 bytes contain header information */
   $"FFFE"  /* version; always -2 for extended version 2 */
   $"0000"  /* reserved */
   $"0048 0000"         /* best horizontal resolution: 72 dpi */
   $"0048 0000"         /* best vertical resolution: 72 dpi */
   $"0002 0002 006E 00AA"  /* optimal source rectangle for 72 dpi horizontal 
                              and 72 dpi vertical resolutions */
   $"0000"  /* reserved */
$"001E"     /* DefHilite opcode to use default hilite color */
$"0001"     /* Clip opcode to define clipping region for picture */
   $"000A"  /* region size */
   $"0002 0002 006E 00AA"  /* bounding rectangle for clipping region */
$"000A"     /* FillPat opcode; fill pattern specified in next 8 bytes */
   $"77DD 77DD 77DD 77DD"  /* fill pattern */
$"0034"     /* fillRect opcode; rectangle specified in next 8 bytes */
   $"0002 0002 006E 00AA"  /* rectangle to fill */
$"000A"     /* FillPat opcode; fill pattern specified in next 8 bytes */
   $"8822 8822 8822 8822"  /* fill pattern */
$"005C"     /* fillSameOval opcode */
$"0008"     /* PnMode opcode */
$  "0008"   /* pen mode data */
$"0071"     /* paintPoly opcode */
   $"001A"  /* size of polygon */
   $"0002 0002 006E 00AA"  /* bounding rectangle for polygon */
   $"006E 0002 0002 0054 006E 00AA 006E 0002"   /* polygon points */
$"00FF"     /* OpEndPic opcode; end of picture */
}