TweetFollow Us on Twitter

PictPack
Volume Number:9
Issue Number:5
Column Tag:4th Dimension

Related Info: Picture Utilities

PictPack - A Package of 4D Externals

Managing picture variables in 4D Externals

By Kent Miller, Arlington, Texas

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

About the author

Kent Miller is the author of 4D Balloon Help and 4D Chooser, both published by Business Network of Oklahoma City. His Email addresses are KPMiller@aol.com or KPMILLER on America Online.

In this article, I will develop a small 4D package that reads PICT files into picture variables, writes picture variables to PICT files, and returns information about 4D picture variables. I will also attempt to illustrate three things:

• How to read and write a PICT file

• How to free up extra memory for your 4D external

• Using a 4D EntryPoint to put a PicHandle into a picture variable

PicHandles and PICT files contain the exact same information except a PICT file has 512 bytes of information at the beginning (to hold information such as the name of the creating program and copyright information). So, if you want to read a PICT, you simply skip the first 512 bytes of the file and then read the rest into a PicHandle. To write one, you just write 512 bytes of something and then write a PicHandle.

The ReadPict Procedure

The ReadPict external takes two parameters, the name of the picture variable to put the picture in and an integer that returns an error. The procedure prompts the user to select a file. When a file is chosen, it reads the picture if it can free up enough memory.

After a 4D database is used for a while, memory gets pretty full and you will probably need to free up some space before reading the picture. I was under the impression that a call to NewHandle made every effort to free up a block of memory, but it seems like I can get a bigger handle more reliably (at least in a 4D external) by calling CompactMem with the amount of memory I want before making the NewHandle call.

A picture field in 4D is made up of two things, a PicHandle and a 6-byte PicEnd record that 4D uses to determine where and how to draw the picture. The PicEnd record is defined like this:

{1}

 PicEnd = record
 origin : Point;
 transferMode : integer;
 end;

The PicEnd record goes (strangely enough) at the end of the picture. Since we had the foresight when we allocated memory to allocate enough for the PicHandle plus the PicEnd, we can just use BlockMove and some fancy pointer arithmetic to put the record at the end of the PicHandle.

{2}

with myPicEnd do
 begin
 origin.h := 0;
 origin.v := 0;
 transfer := srcCopy;
 end;
BlockMove(@myPicEnd, Ptr(ord(thePic^) + 
 GetHandleSize(thePic) - 6), 6);

We use a 4D EntryPoint routine to put the picture back into 4D. 4D has some really convoluted variant record structures it uses to pass information to and from externals. We need two of these structures to put the picture into 4D-the VarRec contains the information we want to send to 4D and the ParmBlock is used whenever you need to make a 4D EntryPoint call.

We fill the VarRec like this:

{3}

       myVarRec.varKind := PICT;
       myVarRec.picSize := GetHandleSize(thePic);
       myVarRec.PP := PicHandle(thePic);

and we fill the ParmBlock like this:

{4}

       Blk4D.Name := PtrList^[1].S^;
       Blk4D.HH := @myVarRec;
       Blk4D.ClearOldVariable := true;

and call the EntryPoint:

{5}

       Call4D(EX_PUT_VARIABLE, Blk4D);

There are 2 reasons I call 4D to put the information into the variable instead of just directly passing a picture variable. In a database that is compiled with 4D Compiler, 4D doesn’t pre-initalize variables it passes you. So, there really isn’t anyway to tell if a variable is valid or not unless you leave the responsibility of initialization to the 4D developer. This isn’t a big deal if it is an integer or longint, but if you think it is a valid PicHandle and try to dispose it, bad things can happen. If you don’t dispose it, you take the chance of the memory becoming lost in the heap. The second reason is assuming the handle is valid, I never can decide what to do with the handle 4D passes. Should I dispose it? What if 4D has another copy of it somewhere? This method eliminates that confusion and I recommend that anytime you need to pass a picture (or text) variable back to 4D you use the EntryPoint routines.

The only other thing of note in this procedure is that once you give 4D the PicHandle, don’t dispose it. After you make the EntryPoint call, 4D becomes responsible for managing the PicHandle. Sample 4D code to call ReadPict is shown in Figure 1.

Figure 1 - Sample 4D Code calling ReadPict

The SavePict Procedure

There are three parameters to the SavePict procedure, the picture variable to save, the creator type for the file, and a place to return an error. I can pass a picture variable this time since I am just going to use it, not replace it. First, I call GetHandleSize to see if the PicHandle from 4D looks valid. If it does, the procedure uses StandardPutFile to get a path for the file. Next, it opens the file and writes 512 bytes of zeros. Then it determines how many bytes of the PicHandle to write by calling GetHandleSize and subtracting 6 bytes for the PicEnd record. Finally, it writes those bytes to the file.

{6}

       count := GetHandleSize(Handle(pic)) - 6;
       err := FSWrite(newFileRefNum, count, Ptr(pic^));

Sample 4D code to call the SavePict procedure is given in Figure 2.

Figure 2 - Sample 4D Code calling SavePict

The ReturnPictInfo Procedure

I have also written a small procedure to get information about pictures for the sake of completeness. I use the System 7 call GetPictInfo to return information about picture fields. Any information could be returned from the package, but I just picked what I think would be the most useful to the user. The parameters to this procedure are the picture variable, 3 integers for the length, width, and depth (number of bits-per-pixel) of the picture, and 2 longints for the size in bytes and number of colors in the picture. Figure 3 shows 4D code to call this procedure.

Figure 3 - Sample 4D Code calling ReturnPictInfo

Loose Ends

All the record definitions and constants I use in the package that aren’t standard Macintosh structures are defined in the Access0 library that is included in the 4D External Kit.

These procedures are lumped into a package, but I suppose that they could’ve just as easily be broken up into separate externals. Being in a package just makes it easier to move them in and out of a database. They can also be grouped together into a popup menu in the 4D design environment using ‘FON#’ and ‘THM#‘ resources. If you have 4D 3.0, you can create these resources with the new 4D External Mover that comes with it. Otherwise those resource templates are included in the 4D External Kit.

This package, like every 4D package, will require 2 resources to be recognized by 4D. The ‘4BNX’ resource groups your package with other resources needed by your package. In our case, the only resource we need besides the ‘4DPX’ (the package itself) is the ‘STR#’ resource that lists the procedures in our package with their parameters. You can create these resources in ResEdit using the templates that come with the 4D External Kit. The ‘4BNX’ and ‘STR#’ resources are included with the source listing in Rez format.

I have used the System 7 file system calls and used the System 7 Picture Utilities Package, so making the package run in System 6 is left as an exercise for the reader.

Think Pascal Project

Figure 4 - The Think Pascal project window

{7}
Source Code
unit PictPack;

interface

 uses
  SANE, Access0, Palettes, PictUtil;

 procedure main (ProcNum: Longint; 
 PtrList: PackageVariablesPtr; var Data: handle; 
 var FuncPtr: PackRetParam);

implementation

 procedure readPict (var thePic: Handle; 
 var theerr: integer);
 FORWARD;

 procedure savePict (var pic: PicHandle; 
 var creator: str255; var err: integer);
 FORWARD;

 procedure ReturnPictInfo (var thePictHandle: PicHandle; 
 var length, width, depth: integer; 
 var colors, size: longint);
 FORWARD;

 procedure main (ProcNum: Longint; 
 PtrList: PackageVariablesPtr; var Data: handle; 
 var FuncPtr: PackRetParam);

  var
   thePic: Handle;
   Blk4D: ParmBlock;
   staticResNum: integer;
   theerr: OSErr;
   myVarRec: VarRec;

 begin
  case ProcNum of
   -1: 
    begin { Init - I’m not allocating any memory}
    end;

   -2: 
    begin { deInit }
    end;

   1: {read a Pict}
    begin
     PtrList^[2].I^ := noErr;
     thePic := nil;
     ReadPict(thePic, PtrList^[2].I^);
     if PtrList^[2].I^ = noErr then  
      begin
       myVarRec.varKind := PICT;
       myVarRec.picSize := GetHandleSize(thePic);
       myVarRec.PP := PicHandle(thePic);
       Blk4D.Name := PtrList^[1].S^;
       Blk4D.HH := @myVarRec;
       Blk4D.ClearOldVariable := true;
       Call4D(EX_PUT_VARIABLE, Blk4D);
       PtrList^[2].I^ := Blk4D.error;
      end;
    end;

   2: {save a Pict}
    begin
     if GetHandleSize(handle(PtrList^[1].P^)) <= 0 then
      PtrList^[4].I^ := -1
     else
      SavePict(PtrList^[1].P^, PtrList^[2].S^, 
 PtrList^[3].I^);
    end;

   3: 
    ReturnPictInfo(PtrList^[1].P^, PtrList^[2].I^, 
 PtrList^[3].I^, PtrList^[4].I^, PtrList^[5].L^, 
 PtrList^[6].L^);
  end;  {case ProcNum}
 end;

 procedure readPict (var thePic: Handle; 
 var theErr: integer);

  var
   reply: StandardFileReply;
   theTypeList: SFTypeList;
   thePicFile: integer;
   bytes, t: longint;
   myPicEnd: PicEnd;
   err: integer;

 begin
  theTypeList[0] := ‘PICT’;
  StandardGetFile(nil, 1, theTypeList, reply);
  if not (reply.sfGood) then
   theErr := -1
  else
   begin
    theErr := FSPOpenDF(reply.sfFile, fsCurPerm, 
 thePicFile);
    if theErr = noErr then
     begin
      theErr := GetEOF(thePicFile, bytes);
      bytes := bytes - 512;
      {need to leave 6 bytes for 4D’s PicEnd}
      t := compactMem(bytes + 6);
      thePic := NewHandle(bytes + 6);
      if thePic = nil then
       theErr := memError
      else
       begin
        Hlock(thePic);
        theErr := SetFPos(thePicFile, 1, 512);
        theErr := FSRead(thePicFile, bytes, thePic^);
        with myPicEnd do  {put on the 4D picEnd record}
         begin
          origin.h := 0;
          origin.v := 0;
            transfer := srcCopy;
         end;
        BlockMove(@myPicEnd, Ptr(ord(thePic^) + 
 GetHandleSize(thePic) - 6), 6);
        HUnLock(thePic);
       end;
      err := FSClose(thePicFile);
     end;
   end;
 end;

 procedure savePict (var pic: PicHandle; 
 var creator: str255; var err: integer);

  var
   theErr: OSErr;
   p: PTR;
   newFileRefNum: integer;
   picSize: longint;
   c: OSType;
   count: longint;
   reply: StandardFileReply;
 
begin
  if pic <> nil then
   begin
    StandardPutFile(‘Save a PICT file ’, 
 ‘PICT from 4D’, reply);
    if (reply.sfGood) then
     begin
      {If the file already exists, replace it}
      theErr := FSpDelete(reply.sfFile); 
      if length(creator) = 4 then
       begin
        BlockMove(@creator[1], @c, 4);
        err := FSpCreate(reply.sfFile, c, 
 ‘PICT’, reply.sfScript);
       end
      else
       err := FSpCreate(reply.sfFile, ‘SPNT’, 
 ‘PICT’, reply.sfScript);
      if err = noErr then
       begin
        err := FSpOpenDF(reply.sfFile, 
 fsRdWrPerm, newFileRefNum);
        if err = noErr then
         begin
          p := NewPtrClear(512);
          if p = nil then
           err := MemError
          else
           begin
            count := 512;
            err := FSWrite(newFileRefNum, count, p);
            if err = noErr then
             begin
              {Take off 6 bytes for the picEnd}
              count := GetHandleSize(Handle(pic)) - 6; 
              err := FSWrite(newFileRefNum, count, 
 ptr(ord(pic^)));
             end;
            DisposPtr(p);
           end;
          err := FSClose(newFileRefNum);
         end;
       end; {NoErr on FSpCreate}
     end;
   end;
 end;

 procedure ReturnPictInfo (var thePictHandle: PicHandle; 
 var length, width, depth: integer; 
 var colors, size: longint);

  var
   thePictInfo: PictInfo;
   saveHandleState: integer;
   theErr: OSErr;

 begin
  saveHandleState := HGetState(Handle(thePictHandle));     
  {save the original state}

  {GetPictInfo can move memory}
  HLock(Handle(thePictHandle));  
  theErr := GetPictInfo(thePictHandle, thePictInfo, 
 returnColorTable, 1, systemMethod, 0);

  if theErr = noErr then
   begin
    if thePictInfo.theColorTable <> nil then
     DisposHandle(Handle(thePictInfo.theColorTable));
    width := thePictInfo.sourceRect.right - 
 thePictInfo.sourceRect.left;
    length := thePictInfo.sourceRect.bottom - 
 thePictInfo.sourceRect.top;
    depth := thePictInfo.depth;
    colors := thePictInfo.uniqueColors;
    size := GetHandleSize(handle(thePictHandle));
  end;
  HSetState(Handle(thePictHandle), saveHandleState);
 end;

end.
Other Resources DeRez-ed

resource ‘4BNX’ (128) {
 { /* array 4BNXArray: 1 elements */
 /* [1] */
 ‘STR#’,/*Type */
 128,   /*Local ID*/
 128    /*Global ID*/
 }
};

resource ‘STR#’ (128) {
 { /* array StringArray: 3 elements */
 /* [1] */
 “ReadPict(&S;&I)”,
 /* [2] */
 “SavePict(&P;&S;&I)”,
 /* [3] */
 “ReturnPictInfo(&P;&I;&I;&I;&L;&L)”
 }
};

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Hopper Disassembler 4.3.16- - Binary dis...
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32- and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about its... Read more
Default Folder X 5.2.2 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more
EtreCheck 4.0.1 - For troubleshooting yo...
EtreCheck is an app that displays the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to... Read more
Carbon Copy Cloner 5.0.9 - Easy-to-use b...
Carbon Copy Cloner backups are better than ordinary backups. Suppose the unthinkable happens while you're under deadline to finish a project: your Mac is unresponsive and all you hear is an ominous,... Read more
QuickBooks 17.2.25.638 R26 - Financial m...
QuickBooks helps you manage your business easily and efficiently. Organize your finances all in one place, track money going in and out of your business, and spot areas where you can save. Built for... Read more
Monosnap 3.4.10 - Versatile screenshot u...
Monosnap lets you capture screenshots, share files, and record video and .gifs! Features Capture Capture full screen, just part of the screen, or a selected window Make your crop area pixel... Read more
Vivaldi 1.14.1077.50 - An advanced brows...
Vivaldi is a browser for our friends. 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... Read more
Viber 8.2.0 - Send messages and make fre...
Viber lets you send free messages and make free calls to other Viber users, on any device and network, in any country! Viber syncs your contacts, messages and call history with your mobile device, so... Read more
QuickBooks 17.2.25.638 R26 - Financial m...
QuickBooks helps you manage your business easily and efficiently. Organize your finances all in one place, track money going in and out of your business, and spot areas where you can save. Built for... Read more
Carbon Copy Cloner 5.0.9 - Easy-to-use b...
Carbon Copy Cloner backups are better than ordinary backups. Suppose the unthinkable happens while you're under deadline to finish a project: your Mac is unresponsive and all you hear is an ominous,... Read more

Latest Forum Discussions

See All

Our top 5 characters from casual RPG Cre...
Creature Quest definitely lives up to its name with a host of collectible creatures based on fantasy tales and world mythologies. To celebrate Creature Quest’s first birthday, we’re going to lay out what we think are the five best characters in the... | Read more »
Around the Empire: What have you missed...
Did you know that Steel Media has a whole swathe of other sites dedicated to all aspects of mobile gaming? Sure you'll get the very best iPhone news, reviews, and opinions right here at 148Apps, but we don't want you missing out on a single piece... | Read more »
All the best games on sale for iPhone an...
Oh hi there, and welcome to our round-up of the best games that are currently on sale for iPhone and iPad. You thought I didn't see you there, did you, skulking behind the bushes? Trust me though, the bushes aren't where the best deals are. The... | Read more »
The Battle of Polytopia Guide - How to H...
A new update just released for The Battle of Polytopia (formerly Super Tribes), which introduces online multiplayer. For all the fans of Midjiwan’s lite take on Civilization, this is certainly welcome news, but playing online isn’t as easy and... | Read more »
Here are the very best mobile games to p...
It's Valentine's Day! Did you get loads of cards and chocolates and other tacky, simple expressions of human affection? Did you send out tat because you find it almost impossible to express emotion unless there's a section dedicated to it at your... | Read more »
Florence (Games)
Florence 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Florence is an interactive storybook from the award-winning lead designer of Monument Valley about the heart-racing highs and... | Read more »
Purrfect Date (Games)
Purrfect Date 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Cats are a lil’ like marmite. Either you absolutely head-over-heels love’ em, or… nahhh, who are we kidding?! Everyone... | Read more »
More monsters to collect and evolve in C...
A laid-back mix of RPG and TCG, Creature Quest is all about building your deck, evolving your creatures and winning in battle. It’s the creation of VC Mobile, set up by Might and Magic producer Jon Van Caneghem. There are elements of that classic... | Read more »
Check out this awesome hands-on with the...
Well, PlayerUnknown's Battlegrounds has come out on mobile. This isn't a clone, this isn't a riff on the battleroyale mechanics of the game, it's the official mobile port by Tencent. But there's a little bit of a hitch. [Read more] | Read more »
Hostage Negotiator (Entertainment)
Hostage Negotiator 1.1.0 Device: iOS Universal Category: Entertainment Price: $3.99, Version: 1.1.0 (iTunes) Description: Official app of the board game by AJ Porfirio and Van Ryder Games. In Hostage Negotiator, you play the part of... | Read more »

Price Scanner via MacPrices.net

Saturday Sale: Amazon offers 13″ 1.8GHz/256GB...
Amazon has the 13″ 1.8GHz/256B Apple MacBook Air on sale today for $250 off MSRP including free shipping: – 13″ 1.8GHz/256GB MacBook Air (MQD42LL/A): $949.99, $250 off MSRP Their price is the lowest... Read more
Roundup of Apple Certified Refurbished 12″ Ma...
Apple has Certified Refurbished 2017 12″ Retina MacBooks available for $200-$240 off the cost of new models. Apple will include a standard one-year warranty with each MacBook, and shipping is free.... Read more
Apple offers Certified Refurbished 10″ and 12...
Apple is now offering Certified Refurbished 2017 10″ and 12″ iPad Pros for $100-$190 off MSRP, depending on the model. An Apple one-year warranty is included with each model, and shipping is free: –... Read more
Apple Canada offers Certified Refurbished Mac...
 Canadian shoppers can save up to $560 on the purchase of a 2017 current-generation MacBook Pro, MacBook, or MacBook Air with Certified Refurbished models at Apple Canada. Apple’s refurbished prices... Read more
Sale! 13″ MacBook Airs for up to $180 off MSR...
B&H Photo has 13″ MacBook Airs on sale for $50-$120 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 13″ 1.8GHz/128GB MacBook Air (MQD32LL/A): $899, $... Read more
Sale! New 8-core iMac Pro for $4799, $200 off...
Adorama has the 8-core iMac Pro on sale for $4799 including free shipping plus NY & NJ sales tax only. Their price is $200 off MSRP, and it’s the currently lowest price available for an iMac Pro. Read more
Sale! Walmart lowers prices even more on 9″ i...
Walmart has lowered their sale price on 9.7″ Apple iPads to $80 off MSRP for a limited time. Sale prices are for online orders only, in-store prices may vary: – 9″ 32GB iPad: $249.99 $80 off – 9″... Read more
Roundup of 13″ MacBook Pro sales, models avai...
B&H Photo has 13″ MacBook Pros on sale for up to $200 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only. Their prices are the lowest available for these... Read more
Roundup of 15″ MacBook Pros sale, models up t...
B&H Photo has 15″ MacBook Pros on sale for up to $200 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 15″ 2.8GHz Touch Bar MacBook Pro Space Gray (... Read more
How to save up to $350 on the purchase of a 2...
B&H Photo has iMacs on sale for up to $150 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 27″ 3.8GHz iMac (MNED2LL/A): $2149 $150 off MSRP – 27″ 3.... Read more

Jobs Board

*Apple* Retail - Multiple Positions - Apple,...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 113501424 Norman, Oklahoma, United States Posted: 15-Feb-2018 Weekly Hours: 40.00 **Job Summary** Are you passionate about Read more
Senior Program Manager - *Apple* Music - Ap...
# Senior Program Manager - Apple Music Job Number: 113393020 Seattle, Washington, United States Posted: 02-Feb-2018 Weekly Hours: 40.00 **Job Summary** Apple is Read more
Hardware Systems Architect - *Apple* Watch...
# Hardware Systems Architect - Apple Watch Job Number: 113410190 Santa Clara Valley, California, United States Posted: 13-Feb-2018 Weekly Hours: 40.00 **Job Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.