TweetFollow Us on Twitter

MacPaint files
Volume Number:1
Issue Number:7
Column Tag:C Workshop

MacPaint file format

By Keith McGreggor

The MacPaint file format is rapidly becoming the standard for transferring graphic information from one application to another. This article will explain that format and show you how to transfer your own images into MacPaint files.

A Little Bit of QuickDraw

The Macintosh’s screen is a bit image. That is, what appears on the screen is actually a collection of consecutive bits in memory that the hardware in the Mac interprets as screen dots (or pixels). If the value of one of these bits is 1, then the pixel corresponding to it will be black. If the bit is 0, then the pixel will be white.

Figure #1. Bits represent pixels

The Mac screen is 512 pixels wide by 342 pixels tall. The bit image in memory takes up 175,104 bits (or 21,888 bytes with 8 bits per byte). We can consider the screen bit image as being 342 rows with 64 bytes per row. Due to the 68000 microprocessor in the Macintosh, every bit image must have an even number of bytes per row, and the rows must begin and end on word boundaries.

In C, the easiest way to define a bit image is with an array of characters. For example, if we wanted to define the Macintosh screen’s bit image, the definition would be:

Figure #2. C definition of a bit image

Bit images are manipulated by Quick- Draw through the use of bitmaps. A bit- map is a structure which points to a bit image and associates a coordinate system with it. The definition of a bitmap is:

Figure #3. C definition of a bitmap

The baseAddr field points to the first byte (character) in the bit image. The rowBytes field contains the number of bytes per row in the bit image. The rectangle bounds provides the coordinate system for the bits. The top left corner of the rectangle is aligned with the first bit of the bit image.

Since we can treat bit images in C as arrays of characters, we don’t always have to display them immediately. You can easily create a picture in a bit image off-screen, and later in your program “stamp” it onto the Mac’s screen.

The Macintosh’s ROM contains several QuickDraw calls that allow you to manipulate bitmaps (on- or off-screen). We’ll look at two of these later in the program.

MacPaint images are kept in the data fork of a MacPaint file. The file is essentially a 512 byte header followed by a bit image that is 576 pixels wide by 720 pixels tall (or 72 bytes by 720 rows).

Figure #4. The MacPaint File Format

The 512 bytes of header contain version information, pattern definitions, and an unused area for future expansion. If you change the contents of this section with care, you can set up your own patterns. If the version number is zero, the default patterns are used. If the number is not zero, then the patterns in the header are used.

Fig.#5.The Paint File Header Format

The MacPaint file bit image is considerably larger than the Macintosh screen’s bit image. In fact, if you were to store a bit image 72 bytes by 720 rows directly onto disk, each MacPaint file would take a minimum of 52K bytes! To make these files smaller, each row of pixels has been compressed using the PackBits routine in the Macintosh ROM. Using PackBits, the typical MacPaint file compresses down to around 10K bytes.

Dipping in the Bit Bucket

To make your program transfer an image into a MacPaint file, you need only to copy the bitmap containing the image into the compressed MacPaint file format. To be able to do this, you need to use two ROM routines, CopyBits and PackBits.

CopyBits transfers the contents of one bitmap into another. If you want, you can specify a mask region in the destination bitmap to prevent CopyBits from destroying the entire image. CopyBits will shrink or expand the contents of the source bitmap to fit the destination bitmap’s rectangle. To call CopyBits from C, use this format:

Figure #6. Calling CopyBits from C

where “copymode” is one of the source transfer modes:

Figure #7. Source Transfer Modes

PackBits compacts a string of bytes by compressing runs of equal bytes. You call PackBits from C like so:

Figure #8. Calling PackBits from C

where “numbytes” is the number of bytes pointed to by “srcPtr.”

Initially, “dstPtr” should point to the first destination byte. The PackBits routine will move “dstPtr” to point to the next available byte. To find out how much space the original bytes were compacted into, you need to subtract the original location of “dstPtr” from its current location.

Fig. #9 How PackBits moves “dstPtr”

About the Program

This program will demonstrate how to “cut” a part of an image into a MacPaint file. It is written for the Consulair Mac C system and Toolkit. You’ll probably need to change things a bit to make it work with other versions of C.

The program opens a single window and draws a few inverted rectangles in it. Then, a gray flashing rectangle will appear and follow the position of the cursor. Use the mouse to position this rectangle where you want, and then press the mouse button. The image inside the rectangle will be cut from the screen (using CopyBits) and transferred into a MacPaint file called “DummyFileName” (using repeated calls to PackBits).

The key routine, MakePaintFile, takes as input a C string containing a filename, and a pointer to a bitmap of arbitrary size. It then creates that file (if possible) on the active disk drive, sets the file signature and type to a MacPaint file type, and compresses that bitmap into the file using PackBits. If the bitmap is smaller than 576 by 720 (as will usually be the case), the bitmap is padded with white space. If the bitmap is larger than 576 by 720, the bitmap is clipped to 576 by 720.

/*
 * MakePaint.h
 *        a C routine to create a MacPaint file
 *        from a given bitmap
 *
 * (c) 1985 by Keith McGreggor for MacTutor
 *       
 */

#define WRITEONLY 7

MakePaintFile( myfilename, mybitmap )
char myfilename[63];
struct ABitMap *mybitmap;
{
 char dstbuf[511],srcbuf[511];
 char *srcPtr;
 char *dstPtr;
 char *mypointer;
 short i,j,dstBytes;
 FILE myfile;
 short t,b,vsize,hsize;
 
// attempt to create the file
 
 myfile = creat( myfilename, WRITEONLY );
 if (myfile != 0) {

// turn the file into a MacPaint file
// and write out a 512 byte header
// full of zeros (we’re not using any of
// our own patterns)

    SetFileSignature(myfilename,’MPNT’); 
    SetFileType(myfilename,’PNTG’);
    for (i = 0; i < 512; i++) fputc(0,myfile);

// figure out how big the bitmap is and set up
// a general pointer to the bit image

    mypointer = mybitmap->baseAddr;
    hsize = mybitmap->rowBytes;
    vsize = (mybitmap->bounds.bottom)
                        - (mybitmap->bounds.top);

// now, write out 720 rows of bytes

    for (j = 1; j <= 720; j++) {

// reinitialize source and destination pointers

 srcPtr = &srcbuf[0];
 dstPtr = &dstbuf[0];

// copy the next row of bytes into srcbuf[],
// clipping or expanding where necessary

 for (i = 0; i < 72; i++) {
        if ((i < hsize) && (j <= vsize)) {
      srcbuf[i] = *mypointer;
           mypointer++;
           }
            else srcbuf[i] = 0;  // 8 white bits
 }

// compress srcbuf[] into dstbuf[]

 #PackBits(&srcPtr,&dstPtr,72);

// figure out how much compression occurred 
// and write those bytes out to the file

 dstBytes= (short)(dstPtr-&dstbuf[0]);
 for (i = 0; i < dstBytes; i++)
                   fputc(dstbuf[i],myfile);
    }

// all 720 lines have been written, so
// close up everything and return

    close(myfile);
 }
}




 /*    CutToPaint.C
  *      A sample program to illustrate
  *      the use of PackBits and CopyBits
  *
  * (c) 1985 by Keith McGreggor for MacTutor
  */
  #Options -N
  #include “Stdio.h”
  #include “MacCdefs.h”
  #include “Window.h”
  #define TRUE 0xFF
  _#define BUTTONNOTPRESSED !#Button()
  #define GRAY &(QD->gray)
  
  // allocate the application’s window
  
  WindowPtr mywindow;
  Rect mywindowrect = { 40, 5, 300, 507 };
  
  // allocate the tracking variables
  
  Rect trackingrect{0,0,100,100};
  short globx,globy,incx,incy;
  
  // allocate a bitmap and bit image to
  // hold the cut bits
  
  struct ABitMap{
   char *baseAddr;
 short  rowbytes;
 Rect bounds;
 };
 
  struct ABitMap targetmap;
  char theactualbits[14][100];
  
  #include “MakePaint.h”
  /* ------------------------------------*/
  // draw some inverted rectangles
  // just to have something to “cut”
  
  DrawSomeStuff()
  {
  Rect temprect;
  short i;
  
  #MoveTo(10,240);
  #DrawString(“\020Press the button!”);
  for (i=0;i<200;i += 10) {
   #SetRect(&temprect,i+20,i+20,i+100,i+40);
 #InvertRect(&temprect);
 }
  }
  
  /*------------------------------------*/
  // Open a window for drawing
  // and do general housekeeping
  
  InitializeOurSystem()
  {
  #InitDialogs(0);
  mywindow = (WindowPtr)#NewWindow(0,  &mywindowrect,”\021A Window for 
bits”,  TRUE,0,-1,TRUE,0);
  #SetPort(mywindow);
  DrawSomeStuff();
  #FlushEvents(-1,0);
  #InitCursor();
  #PenSize(2,2);   // set up pen for
  #PenMode(patXor);  // drawing the
  #PenPat(GRAY);   // ghost rectange
  }

  /*------------------------------------*/
  // Draw the ghost rectangle
  
  DrawCurrentPosition()
  {
  #FrameRect(&trackingrect);
  }

  /*--------------------------------------*/
  // Find out where the mouse is and
  // update global variables
  
  GetNewMouse()
  {
  Point mypoint;
  
  #GetMouse(&mypoint);
  #GlobalToLocal(&mypoint);
  incx = mypoint.h-globx;
  incy = mypoint.v-globy;
  globx = mypoint.h;
  globy = mypoint.v;
  }

  /*------------------------------------*/
  // move the ghost rectange to track
  // the motion of the mouse
  
  UpdatePostion()
  {
  #OffsetRect(&trackingrect,incx,incy);
  }
  
  /*------------------------------------*/
  // First, move around a ghost rectange
  // until the button is pressed.
  // Then, create a bitmap and copy
  // whatever is inside the rectange to
  // the bitmap.
  
  CutARectangle()
  {
  globx = 0;
  globy = 0;
  while (BUTTONNOTPRESSED) {
   DrawCurrentPosition();
 GetNewMouse();
 DrawCurrentPosition();
 UpdatePosition();
  }
  #FlushEvents(-1,0);
  #LocalToGlobal(&trackingrect.topleft);
  #LocalToGlobal(&trackingrect.botRight);
  targetmap.baseAddr = &theactualbits[0][0];
  targetmap.rowBytes = 14;
  targetmap.bounds.left = 0;
  targetmap.bounds.top = 0;
  targetmap.bounds.right = trackingrect.right-trackingrect.left;
  targetmap.bounds.bottom = trackingrect.bottom-   trackingrect.top;
  
  // mywindow -> portBits is the Macintosh screen bit image
  
  #CopyBits(&(mywindow->portBits), &targetmap,
   &trackingrect,
 &(targetmap.bounds),
 srcCopy,
 0);
  }
  
  /*------------------------------------*/
  // call makepaintfile to save the
  // bitmap away as a macpaint file
  // named “dummyfilename”
  // (note: see MakePaint.h listing)
  
  SaveItAway()
  {
  MakePaintFile(“DummyFileName”,&targetmap);
  }
  
  /*----------------------------------*/
  // Our main program
  
  main()
  {
   InitializeOurSystem();
 CutARectangle();
 SaveItAway();
 #ExitToShell();
  }
 
AAPL
$118.93
Apple Inc.
-0.07
MSFT
$47.81
Microsoft Corpora
+0.06
GOOG
$541.83
Google Inc.
+1.46

MacTech Search:
Community Search:

Software Updates via MacUpdate

Adobe Photoshop Elements 13.0 - Consumer...
Adobe Photoshop Elements 12--the #1 selling consumer photo editing software--helps you edit pictures with powerful, easy-to-use options and share them via print, the web, Facebook, and more.Version... Read more
Skype 7.2.0.412 - Voice-over-internet ph...
Skype allows you to talk to friends, family and co-workers across the Internet without the inconvenience of long distance telephone charges. Using peer-to-peer data transmission technology, Skype... Read more
HoudahSpot 3.9.6 - Advanced file search...
HoudahSpot is a powerful file search tool built upon MacOS X Spotlight. Spotlight unleashed Create detailed queries to locate the exact file you need Narrow down searches. Zero in on files Save... Read more
RapidWeaver 6.0.3 - Create template-base...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
iPhoto Library Manager 4.1.10 - Manage m...
iPhoto Library Manager lets you organize your photos into multiple iPhoto libraries. Separate your high school and college photos from your latest summer vacation pictures. Or keep some photo... Read more
iExplorer 3.5.1.9 - View and transfer al...
iExplorer is an iPhone browser for Mac lets you view the files on your iOS device. By using a drag and drop interface, you can quickly copy files and folders between your Mac and your iPhone or... Read more
MacUpdate Desktop 6.0.3 - Discover and i...
MacUpdate Desktop 6 brings seamless 1-click installs and version updates to your Mac. With a free MacUpdate account and MacUpdate Desktop 6, Mac users can now install almost any Mac app on macupdate.... Read more
SteerMouse 4.2.2 - Powerful third-party...
SteerMouse is an advanced driver for USB and Bluetooth mice. It also supports Apple Mighty Mouse very well. SteerMouse can assign various functions to buttons that Apple's software does not allow,... Read more
iMazing 1.1 - Complete iOS device manage...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
PopChar X 7.0 - Floating window shows av...
PopChar X helps you get the most out of your font collection. With its crystal-clear interface, PopChar X provides a frustration-free way to access any font's special characters. Expanded... Read more

Latest Forum Discussions

See All

Mystery Case Files: Dire Grove, Sacred G...
Mystery Case Files: Dire Grove, Sacred Grove HD Review By Jennifer Allen on November 28th, 2014 Our Rating: iPad Only App - Designed for the iPad A decent new installment for the popular Mystery Case Files series.   | Read more »
Castaway Paradise – Tips, Tricks, and St...
Ahoy there, castaways: Were you curious about our own thoughts regarding this pristine shipwreck? Check out our Castaway Paradise review! Castaway Paradise is out for iOS, finally giving mobile gamers the opportunity to enjoy the idyllic lifestyle... | Read more »
Castaway Paradise VIP Subs are on Sale f...
Castaway Paradise VIP Subs are on Sale for a Limited Time, and a Special Holiday Update is Coming Soon Posted by Rob Rich on November 28th, 2014 [ | Read more »
Primitive Review
Primitive Review By Jordan Minor on November 28th, 2014 Our Rating: :: FOLK ARTUniversal App - Designed for iPhone and iPad True to its name, Primitive is about as straightforward as runners get.   | Read more »
7 tips to get ahead of the competition i...
7 tips to get ahead of the competition in Dynasty of Dungeons Posted by Simon Reed on November 28th, 2014 [ permalink ] Playcrab has launched their action-packed new dungeon crawler, Dynasty of Dungeons, today. | Read more »
Master of Tea Kung Fu Review
Master of Tea Kung Fu Review By Jordan Minor on November 28th, 2014 Our Rating: :: ONE DROP RULESUniversal App - Designed for iPhone and iPad Master of Tea Kung Fu is a creative and complex caffeinated brawler.   | Read more »
Monster Strike Review
Monster Strike Review By Campbell Bird on November 28th, 2014 Our Rating: :: BILLIARD STRATEGYUniversal App - Designed for iPhone and iPad Collect monsters and battle by flinging them across the battlefield in this strangely... | Read more »
Proun+ Review
Proun+ Review By Jennifer Allen on November 28th, 2014 Our Rating: :: TWITCHY RACINGUniversal App - Designed for iPhone and iPad Twitchy racing aplenty in Proun+, an enjoyably tricky title.   | Read more »
Lucha Amigos (Games)
Lucha Amigos 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Forget Ninja Turtles, and meet Wrestlers Turtles! Crazier, Spicier and…Bouncier! Sling carapaces of 7 Luchadores to knock all... | Read more »
Record of Agarest War Zero (Games)
Record of Agarest War Zero 1.0 Device: iOS Universal Category: Games Price: $7.99, Version: 1.0 (iTunes) Description: HyperDevbox Holiday Turkey Black Friday Special Pricing! To celebrate the opening of the holiday season HyperDevbox... | Read more »

Price Scanner via MacPrices.net

Up To 75% Off Infovole Text Apps Over Black F...
Infovole’s entire range of apps, including the Textkraft family of word processors for iPads and iPhones, is being offered at 50-75% off over the Black Friday and Cyber Monday weekend. The five-day... Read more
Black Friday: Up to $60 off Mac minis, NY tax...
 B&H Photo has new 2014 Mac minis on sale for up to $60 off MSRP as part of their Black Friday sale. Shipping is free, and B&H charges NY sales tax only: - 1.4GHz Mac mini: $449.99 $50 off... Read more
Black Friday: 27-inch 5K iMac for $2299, save...
 B&H Photo continues to offer Black Friday sale prices on the 27″ 3.5GHz 5K iMac, in stock today and on sale for $2299 including free shipping plus NY sales tax only. Their price is $200 off MSRP... Read more
Karalux Announces 24K Gold-Plated iPhone 6
Karalux, a Vietnam-based jewellery firm, has launched a unique 24 karat gold-plated iPhone 6 version with gold-cast monolithic dragon on its back panel. The real 24 karat gold plated enclosure doesn’... Read more
Black Friday: 13-inch 2.6GHz Retina MacBook P...
 B&H Photo has lowered their price for the 13″ 2.6GHz/128GB Retina MacBook Pro to $1159 for Black Friday. That’s $140 off MSRP, and it’s the lowest price for this model (except for Apple’s $1099... Read more
View all the Black Friday sales on our Mac Pr...
We’ve updated our Mac Price Trackers with the latest information on prices, bundles, and availability on systems from Apple’s authorized internet/catalog resellers. View Black Friday sale prices at a... Read more
Black Friday: 11-inch MacBook Air for $779, s...
 Best Buy has lowered their price for the 2014 11″ 1.4GHz/128GB MacBook Air to $779.99 for Black Friday. That’s $120 off MSRP. Choose free shipping or free local store pickup (if available). Sale... Read more
Apple Store Black Friday sale for 2014: $100...
BLACK FRIDAY The Apple Store has posted their Black Friday deals for 2014. Receive a $100 PRODUCT(RED) branded iTunes gift card with the purchase of select Macs, $50 with iPads, and $25 with iPods,... Read more
Black Friday: 15% off iTunes Gift Cards
Staples is offering 15% off $50 and $100 iTunes Gift Cards on their online store as part of their Black Friday sale. Click here for more information. Shipping is free. Best Buy is offering $100... Read more
BEVL Releases Dock Tailored for iPhone 6 and...
Seattle based BEVL has released their first product: an iPhone dock that is divergent in build quality, rock-solid function and visual simplicity to complement the iPhone. BEVL is now accepting... Read more

Jobs Board

*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.