Graphics GET and PUT Require Integer or LONG Array; Example (37308)

SUMMARY

Page 208 of the "Microsoft QuickBasic 4.0: Basic Language Reference" manual states the following:

Unless the array type is integer or long, the contents of an array after a [graphics] GET appear meaningless when inspected directly.

This statement also applies when saving the elements of the array to a file. Unless the array type is integer or long, the resulting picture, when read back from disk, will be distorted.

This information applies to Microsoft QuickBasic Versions 4.00, 4.00b, and 4.50, to Microsoft Basic Compiler Versions 6.00 and 6.00b for MS-DOS and MS OS/2, and to Microsoft Basic PDS Version 7.00 for MS-DOS and MS OS/2.

MORE INFORMATION

The program below will display a picture, save it to disk, read it back from disk, and re-display the picture. If the "picture()" array is of integer type, the program will work as expected. If it is of single type, the resulting picture will be distorted.

The following is a code example:

CONST picSize = 16383
DIM picture(picSize) AS SINGLE   ' Change to INTEGER

SCREEN 3  ' SCREEN 3 is for Hercules. Use SCREEN 2 for CGA card.
FOR x = 1 TO 150 STEP 2.5          ' Draw a simple picture
  LINE (x + 300, x)-(300 - x, 300 - x), 7, B
NEXT

GET (30, 0)-(450, 300), picture

OPEN "temp.pic" FOR OUTPUT AS #1   ' Save the picture
FOR i = 0 TO picSize
  PRINT #1, picture(i)
NEXT i
CLOSE #1

OPEN "temp.pic" FOR INPUT AS #1    ' Load the picture back
FOR i = 0 TO picSize
  INPUT #1, picture(i)
NEXT i

CLS
PUT (5, 5), picture                ' Display the picture