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

jAlbum Pro 12.6.4 - Organize your digita...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code!... Read more
jAlbum 12.6.4 - Create custom photo gall...
With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly, with pro results Simply drag and drop photos into groups, choose a design... Read more
Microsoft Remote Desktop 8.0.16 - Connec...
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
Spotify 1.0.4.90. - Stream music, create...
Spotify is a streaming music service that gives you on-demand access to millions of songs. Whether you like driving rock, silky R&B, or grandiose classical music, Spotify's massive catalogue puts... Read more
djay Pro 1.1 - Transform your Mac into a...
djay Pro provides a complete toolkit for performing DJs. Its unique modern interface is built around a sophisticated integration with iTunes and Spotify, giving you instant access to millions of... Read more
Vivaldi 1.0.118.19 - Lightweight browser...
Vivaldi browser. In 1994, two programmers started working on a web browser. Our idea was to make a really fast browser, capable of running on limited hardware, keeping in mind that users are... Read more
Stacks 2.6.11 - New way to create pages...
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
xScope 4.1.3 - Onscreen graphic measurem...
xScope is powerful set of tools that are ideal for measuring, inspecting, and testing on-screen graphics and layouts. Its tools float above your desktop windows and can be accessed via a toolbar,... Read more
Cyberduck 4.7 - FTP and SFTP browser. (F...
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more
Labels & Addresses 1.7 - Powerful la...
Labels & Addresses is a home and office tool for printing all sorts of labels, envelopes, inventory labels, and price tags. Merge-printing capability makes the program a great tool for holiday... Read more

Discover Your Reflexes With Minimalist G...
Discover O, BYOF Studios, may look simple at first with its' color matching premise and swipe controls, but as you speed up the task becomes more daunting. [Read more] | Read more »
Here's Another Roundup of Notable A...
Now that the Apple Watch is publically available (kind of), even more apps and games have been popping up for it. Some of them are updates to existing software, others are brand new. The main thing is that they're all for the Apple Watch, and if you... | Read more »
Use Batting Average and the Apple Watch...
Batting Average, by Pixolini, is designed to help you manage your statistics. Every time you go to bat, you can use your Apple Watch to track  your swings, strikes, and hits. [Read more] | Read more »
Celebrate Studio Pango's 3rd Annive...
It is time to party, Pangoland pals! Studio Pango is celebrating their 3rd birthday and their gift to you is a new update to Pangoland. [Read more] | Read more »
Become the World's Most Important D...
Must Deliver, by cherrypick games, is a top-down endless-runner witha healthy dose of the living dead. [Read more] | Read more »
SoundHound + LiveLyrics is Making its De...
SoundHound Inc. has announced that SoundHound + LiveLyrics, will be one of the first third-party apps to hit the Apple Watch. With  SoundHound you'll be able to tap on your watch and have the app recognize the music you are listening to, then have... | Read more »
Adobe Joins the Apple Watch Lineup With...
A whole tidal wave of apps are headed for the Apple Watch, and Adobe has joined in with 3 new ways to enhance your creativity and collaborate with others. The watch apps pair with iPad/iPhone apps to give you total control over your Adobe projects... | Read more »
Z Steel Soldiers, Sequel to Kavcom'...
Kavcom has released Z Steel Soldiers, which continues the story of the comedic RTS originally created by the Bitmap Brothers. [Read more] | Read more »
Seene Lets You Create 3D Images With You...
Seene, by Obvious Engineering, is a 3D capture app that's meant to allow you to create visually stunning 3D images with a tap of your finger, and then share them as a 3D photo, video or gif. [Read more] | Read more »
Lost Within - Tips, Tricks, and Strategi...
Have you just downloaded Lost Within and are you in need of a guiding hand? While it’s not the toughest of games out there you might still want some helpful tips to get you started. [Read more] | Read more »

Price Scanner via MacPrices.net

Zoho Business Apps for Apple Watch Put Select...
Pleasanton, California based Zoho has launched Zoho Business Apps for Apple Watch, a line of apps that extends Zoho business applications to let users perform select functions from an Apple Watch.... Read more
Universal Stylus Initiative Launched to Creat...
OEMs, stylus and touch controller manufacturers have announced the launch of Universal Stylus Initiative (USI), a new organization formed to develop and promote an industry specification for an... Read more
Amazon Shopping App for Apple Watch
With the new Amazon shopping app for Apple Watch, Amazon customers with one of the wearable devices can simply tap the app on the watch to purchase items in seconds, or save an idea for later. The... Read more
Intel Compute Stick: A New Mini-Computing For...
The Intel Compute Stick, a new pocket-sized computer based on a quad-core Intel Atom processor running Windows 8.1 with Bing, is available now through Intel Authorized Dealers across much of the... Read more
Heal to Launch First One-Touch House Call Doc...
Santa Monica, California based Heal, a pioneer in on-demand personal health care services — will offer the first one-touch, on-demand house call doctor app for the Apple Watch. Heal’s Watch app,... Read more
Mac Notebooks: Avoiding MagSafe Power Adapter...
Apple Support says proper usage, care, and maintenance of Your Mac notebook’s MagSafe power adapter can substantially increase the the adapter’s service life. Of course, MagSafe itself is an Apple... Read more
12″ Retina MacBook In Shootout With Air And P...
BareFeats’ rob-ART morgan has posted another comparison of the 12″ MacBook with other Mac laptops, noting that the general goodness of all Mac laptops can make which one to purchase a tough decision... Read more
FileMaker Go for iPad and iPhone: Over 1.5 Mi...
FileMaker has announced that its FileMaker Go for iPad and iPhone app has surpassed 1.5 million downloads from the iTunes App Store. The milestone confirms the continued popularity of the FileMaker... Read more
Sale! 13-inch 2.7GHz Retina MacBook Pro for $...
 Best Buy has the new 2015 13″ 2.7GHz/128GB Retina MacBook Pro on sale for $1099 – $200 off MSRP. Choose free shipping or free local store pickup (if available). Price for online orders only, in-... Read more
Minimalist MacBook Confirms Death of Steve Jo...
ReadWrite’s Adriana Lee has posted a eulogy for the “Digital Hub” concept Steve Jobs first proposed back in 2001, declaring the new 12-inch MacBook with its single, over-subscribed USB-C port to be... Read more

Jobs Board

*Apple* Client Systems Solution Specialist -...
…drive revenue and profit in assigned sales segment and/or region specific to the Apple brand and product sets. This person will work directly with CDW Account Managers 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* Support Technician IV - Jack Henry a...
Job Description Jack Henry & Associates is seeking an Apple Support Technician. This position while acting independently, ensures the proper day-to-day control of Read more
*Apple* Client Systems Solution Specialist -...
…drive revenue and profit in assigned sales segment and/or region specific to the Apple brand and product sets. This person will work directly with CDW Account Managers Read more
*Apple* Software Support - Casper (Can work...
…experience . Full knowledge of Mac OS X and prior . Mac OSX / Server . Apple Remote Desktop . Process Documentation . Ability to prioritize multiple tasks in a fast pace Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.