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();
  }
 

Community Search:
MacTech Search:

Software Updates via MacUpdate

calibre 2.17 - Complete e-library manage...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more
OmniGraffle Pro 6.1.2 - Create diagrams,...
OmniGraffle Pro helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use... Read more
OmniGraffle 6.1.2 - Create diagrams, flo...
OmniGraffle helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use Graffle to... Read more
RoboForm 2.0.2 - Password manager; syncs...
RoboForm is a password manager that offers one-click login, mobile syncing, easy form filling, and reliable security. Password Manager. RoboForm remembers your passwords so you don't have to! Just... Read more
Apple MainStage 3.1 - Live performance t...
Love the sound you got on your recording? MainStage 3 makes it easy to bring all the same instruments and effects to the stage. Everything from the Sound Library and Smart Controls you're familiar... Read more
Freeway Pro 7.0.2 - Drag-and-drop Web de...
Freeway Pro lets you build websites with speed and precision... without writing a line of code! With its user-oriented drag-and-drop interface, Freeway Pro helps you piece together the website of... Read more
A Better Finder Rename 9.44 - File, phot...
A Better Finder Rename is the most complete renaming solution available on the market today. That's why, since 1996, tens of thousands of hobbyists, professionals and businesses depend on A Better... Read more
Stacks 2.6.9 - New way to create pages i...
Stacks is a new way to create pages in RapidWeaver. It's a plugin designed to combine drag-and-drop simplicity with the power of fluid layout. Features: Fluid Layout: Stacks lets you build pages... Read more
Sid Meier's Civilization: Beyond Ea...
Sid Meier's Civilization: Beyond Earth is a new science-fiction-themed entry into the award-winning Civilization series. Set in the future, global events have destabilized the world leading to a... Read more
Logic Pro X 10.1 - Music creation and au...
Apple Logic Pro X is the most advanced version of Logic ever. Sophisticated new tools for professional songwriting, editing, and mixing are built around a modern interface that's designed to get... Read more

Choice Provisions is Set to Launch Destr...
Choice Provisions is Set to Launch Destructamundo on iOS This Month Posted by Tre Lawrence on January 23rd, 2015 [ permalink ] Choice Provisions – home stable to | Read more »
King of Thieves – An Interview With Zept...
Ahead of the release of ZeptoLab’s King of Thieves, we were able to ask ZeptoLab’s co-founder, Semyon Voinov, a few questions about the inspiration behind the game and what that means for the Cut the Rope franchise. | Read more »
Handle Review
Handle Review By Jennifer Allen on January 23rd, 2015 Our Rating: :: SPEEDY ORGANIZINGUniversal App - Designed for iPhone and iPad Handle is a very convenient way of juggling your emails, To Do list, and Calendar all through one... | Read more »
The New Disney Inquizitive App Offers a...
The New Disney Inquizitive App Offers a Place for Fans to Take Disney Quizzes Posted by Tre Lawrence on January 23rd, 2015 [ permalink ] | Read more »
Hands-On With Cut the Rope Developer Zep...
Marking quite a departure from ZeptoLab’s past successes, namely the Cut The Rope series, King of Thieves is shaping up to be quite promising. Due for release in February, we were lucky enough to have some time with a preview build to see exactly... | Read more »
Fast Fishing Review
Fast Fishing Review By Jennifer Allen on January 23rd, 2015 Our Rating: :: LIVES UP TO ITS NAMEUniversal App - Designed for iPhone and iPad Fishing is far from relaxing in Fast Fishing, but it is fun.   | Read more »
The LEGO Movie Video Game is Available N...
The LEGO Movie Video Game is Available Now for iOS Posted by Ellis Spice on January 23rd, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Satellina Review
Satellina Review By Jennifer Allen on January 23rd, 2015 Our Rating: :: TWITCHY BUT TACTICALUniversal App - Designed for iPhone and iPad Satellina requires quick thinking and twitchy fingers, and it’s pretty fun.   | Read more »
Tail Drift, the Crazy 360 Degree Flyer,...
Tail Drift, the Crazy 360 Degree Flyer, Has Gone Free-to-Play in a New Update Posted by Jessica Fisher on January 22nd, 2015 [ permalink ] | Read more »
PureSkate 2 Review
PureSkate 2 Review By Tre Lawrence on January 22nd, 2015 Our Rating: :: ALMOST ALL AIRUniversal App - Designed for iPhone and iPad PureSkate 2 lets one’s fingers do the skateboarding.   | Read more »

Price Scanner via MacPrices.net

College Student Deals are back, additional $5...
Take an additional $50 off all MacBooks and iMacs at Best Buy Online with their College Students Deals Savings, valid through April 11, 2015. Anyone with a valid .EDU email address can take advantage... Read more
iPhone 6 and 6 Plus GIve Apple Half Of US Mob...
Chicago-based Consumer Intelligence Research Partners, LLC (CIRP) have released analysis of the results of its research on mobile phone manufacturers for the calendar quarter that ended December 31,... Read more
Save $100 on MacBook Airs with 256GB of stora...
B&H Photo has 256GB MacBook Airs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 1.4GHz/256GB MacBook Air: $999 $100 off MSRP - 13″ 1.4GHz/256GB MacBook... Read more
21-inch 2.7GHz iMac on sale for $1179, save $...
B&H Photo has the 21″ 2.7GHz iMac on sale for $1179 including free shipping plus NY sales tax only. Their price is $120 off MSRP, and it’s the lowest price available for this model from any... Read more
iPhone Usage Rates by State Correlate With Ed...
Chitika Insights notes that despite iPhones being the largest source of smartphone Internet traffic in North America, their latest study finds a relatively high degree of variation of iPhone usage... Read more
ProGearX Extendable Pole “Pov/Selfie Stick” M...
There’s something inescapably narcissistic about the concept of selfies as they’ve developed as a smartphone-driven social (particularly social media) phenomenon that rubs me the wrong way. However,... Read more
iPad Air 2 on sale for up to $100 off MSRP, 2...
 Best Buy has iPad Air 2s on sale for up to $100 off MSRP on their online store for the next two days. Choose free shipping or free local store pickup (if available). Sale prices available for online... Read more
Roundup of Apple refurbished MacBook Pros and...
The Apple Store has Apple Certified Refurbished 2014 MacBook Pros and MacBook Airs available for up to $400 off the cost of new models. An Apple one-year warranty is included with each model, and... Read more
Sale! 13-inch 2.8GHz Retina MacBook Pro for $...
 B&H Photo has the 13″ 2.8GHz Retina MacBook Pro on sale for $1599 including free shipping plus NY sales tax only. Their price is $200 off MSRP, and it’s the lowest price available for this model... Read more
Next OS X/iOS Version Upgrades Should Concent...
On stage at Apple’s World Wide Developers’ Conference in June 2009, Bertrand Serlet, the company’s Senior Vice President of Software Engineering at the time, announced that the forthcoming OS X... Read more

Jobs Board

Business Development Manager - *Apple* Pay...
**Job Summary** Apple Pay is seeking an experienced business development manager to support the identification, recruitment, negotiation and ongoing management of Read more
*Apple* Solutions Consultant (ASC)- Retail S...
**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 - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
*Apple* Lead Operator, GSOC - Apple (United...
**Job Summary** Apple is seeking an exceptional, customer service oriented and experienced persons to fulfill the role of Apple Lead Operator (ALO) as part of the Read more
Order Support Supervisor- *Apple* Online Sto...
**Job Summary** The Apple Online Store (AOS) Order Administration team is looking for an Order Support Supervisor to manage and lead a team of Specialists through the Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.