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
$97.67
Apple Inc.
+0.64
MSFT
$44.50
Microsoft Corpora
+0.10
GOOG
$589.02
Google Inc.
-4.33

MacTech Search:
Community Search:

Software Updates via MacUpdate

TinkerTool 5.3 - Expanded preference set...
TinkerTool is an application that gives you access to additional preference settings Apple has built into Mac OS X. This allows to activate hidden features in the operating system and in some of the... Read more
Audio Hijack Pro 2.11.0 - Record and enh...
Audio Hijack Pro drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio with Audio Hijack... Read more
Intermission 1.1.1 - Pause and rewind li...
Intermission allows you to pause and rewind live audio from any application on your Mac. Intermission will buffer up to 3 hours of audio, allowing users to skip through any assortment of audio... Read more
Autopano Giga 3.6 - Stitch multiple imag...
Autopano Giga allows you to stitch 2, 20, or 2,000 images. Version 3.0 integrates impressive new features that will definitely make you adopt Autopano Pro or Autopano Giga: Choose between 9... Read more
Airfoil 4.8.7 - Send audio from any app...
Airfoil allows you to send any audio to AirPort Express units, Apple TVs, and even other Macs and PCs, all in sync! It's your audio - everywhere. With Airfoil you can take audio from any... Read more
Microsoft Remote Desktop 8.0.8 - Connect...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more
xACT 2.30 - Audio compression toolkit. (...
xACT stands for X Aaudio Compression Toolkit, an application that encodes and decodes FLAC, SHN, Monkey’s Audio, TTA, Wavpack, and Apple Lossless files. It also can encode these formats to MP3, AAC... Read more
Firefox 31.0 - Fast, safe Web browser. (...
Firefox for Mac offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals... Read more
Little Snitch 3.3.3 - Alerts you to outg...
Little Snitch gives you control over your private outgoing data. Track background activityAs soon as your computer connects to the Internet, applications often have permission to send any... Read more
Thunderbird 31.0 - Email client from Moz...
As of July 2012, Thunderbird has transitioned to a new governance model, with new features being developed by the broader free software and open source community, and security fixes and improvements... Read more

Latest Forum Discussions

See All

Reddme for iPhone - The Reddit Client (...
Reddme for iPhone - The Reddit Client 1.0 Device: iOS iPhone Category: News Price: $.99, Version: 1.0 (iTunes) Description: Reddme for iPhone is an iOS 7-optimized Reddit client that offers a refreshing new way to experience Reddit... | Read more »
Jacob Jones and the Bigfoot Mystery : Ep...
Jacob Jones and the Bigfoot Mystery : Episode 2 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Jacob Jones is back in Episode 2 of one of Apples 'Best of 2013' games and an App Store... | Read more »
New Trailer For Outcast Odyssey, A New K...
New Trailer For Outcast Odyssey, A New Kind of Card Battler Posted by Jennifer Allen on July 25th, 2014 [ permalink ] Out this Fall is a new kind of card battle game: Outcast Odyssey. | Read more »
Garfield: Survival of the Fattest Coming...
Garfield: Survival of the Fattest Coming to iOS this Fall Posted by Jennifer Allen on July 25th, 2014 [ permalink ] Who loves lasagna? Me. Also everyone’s favorite grumpy fat cat, Garfield. | Read more »
Happy Flock Review
Happy Flock Review By Andrew Fisher on July 25th, 2014 Our Rating: :: HERD IT ALL BEFOREUniversal App - Designed for iPhone and iPad Underneath the gloss of Happy Flock’s visuals is a game of very little substance. It’s cute, but... | Read more »
Square Register Updates Adds Offline Pay...
Square Register Updates Adds Offline Payments Posted by Ellis Spice on July 25th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Looking For Group – Hearthstone’s Curse...
For the first time since its release (which has thankfully been a much shorter window for iPad players than their PC counterparts), Blizzard’s wildly successful Hearthstone: Heroes of Warcraft CCG is sporting some brand new content: the single... | Read more »
Poptile Review
Poptile Review By Jennifer Allen on July 25th, 2014 Our Rating: :: SIMPLY FUNUniversal App - Designed for iPhone and iPad Simple yet a little bit glorious, Poptile is a satisfying entertaining puzzle game with oodles of the ‘one... | Read more »
Modern Combat 5: Blackout Review
Modern Combat 5: Blackout Review By Brittany Vincent on July 25th, 2014 Our Rating: :: LESS QQ, MORE PEW PEWUniversal App - Designed for iPhone and iPad The fifth entry into the blockbuster Modern Combat series is what mobile... | Read more »
Watch and Share Mobile Gameplay Videos W...
Watch and Share Mobile Gameplay Videos With Kamcord Posted by Jennifer Allen on July 25th, 2014 [ permalink ] iPhone App - Designed for the iPhone, compatible with the iPad | Read more »

Price Scanner via MacPrices.net

iMacs on sale for $150 off MSRP, $250 off for...
Best Buy has iMacs on sale for up to $160 off MSRP for a limited time. Choose free home shipping or free instant local store pickup (if available). Prices are valid for online orders only, in-store... Read more
Mac minis on sale for $100 off MSRP, starting...
Best Buy has Mac minis on sale for $100 off MSRP. Choose free shipping or free instant local store pickup. Prices are for online orders only, in-store prices may vary: 2.5GHz Mac mini: $499.99 2.3GHz... Read more
Global Tablet Market Grows 11% in Q2/14 Notwi...
Worldwide tablet sales grew 11.0 percent year over year in the second quarter of 2014, with shipments reaching 49.3 million units according to preliminary data from the International Data Corporation... Read more
New iPhone 6 Models to Have Staggered Release...
Digitimes’ Cage Chao and Steve Shen report that according to unnamed sources in Apple’s upstream iPhone supply chain, the new 5.5-inch iPhone will be released several months later than the new 4.7-... Read more
New iOS App Helps People Feel Good About thei...
Mobile shoppers looking for big savings at their favorite stores can turn to the Goodshop app, a new iOS app with the latest coupons and deals at more than 5,000 online stores. In addition to being a... Read more
Save on 5th generation refurbished iPod touch...
The Apple Store has Apple Certified Refurbished 5th generation iPod touches available starting at $149. Apple’s one-year warranty is included with each model, and shipping is free. Many, but not all... Read more
What Should Apple’s Next MacBook Priority Be;...
Stabley Times’ Phil Moore says that after expanding its iMac lineup with a new low end model, Apple’s next Mac hardware decision will be how it wants to approach expanding its MacBook lineup as well... Read more
ArtRage For iPhone Painting App Free During C...
ArtRage for iPhone is currently being offered for free (regularly $1.99) during Comic-Con San Diego #SDCC, July 24-27, in celebration of the upcoming ArtRage 4.5 and other 64-bit versions of the... Read more
With The Apple/IBM Alliance, Is The iPad Now...
Almost since the iPad was rolled out in 2010, and especially after Apple made a 128 GB storage configuration available in 2012, there’s been debate over whether the iPad is a serious tool for... Read more
MacBook Airs on sale starting at $799, free s...
B&H Photo has the new 2014 MacBook Airs on sale for up to $100 off MSRP for a limited time. Shipping is free, and B&H charges NY sales tax only. They also include free copies of Parallels... 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
*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
Sr Software Lead Engineer, *Apple* Online S...
Sr Software Lead Engineer, Apple Online Store Publishing Systems Keywords: Company: Apple Job Code: E3PCAK8MgYYkw Location (City or ZIP): Santa Clara Status: Full 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.