BSAVE - QB64Official/qb64 GitHub Wiki

BSAVE saves the contents of an image array to a BINARY file.

Legacy Support

  • QB64 can save larger arrays directly to binary files using PUT # and GET # without BSAVE. For that reason, use of BSAVE is no longer recommended practice but is supported to maintain compatibility with legacy code.

Syntax

BSAVE saveFile$, VARPTR(array(index)), fileSize&

Parameter(s)

  • saveFile$ is the STRING file name of the file designated to be created.
  • array(index) is the image arrays that already holds the GET (graphics statement) image data.
  • fileSize& must be a bit over twice the size of the elements used in an INTEGER Arrays.

Description

  • To place image data into the array, use GET (graphics statement) to store a box area image of the screen.
  • SCREEN 12 can only GET 1/3 of the screen image at one time using a 26K array.
  • Image arrays are DIMensioned as INTEGER. Use DEFINT when working with large graphic arrays.
  • Any arrays can be saved, but image arrays are most common.
  • DEF SEG = VARSEG must be used to designate the array segment position in memory.
  • VARPTR returns the array index offset of the memory segment. Array sizes are limited to 32767 Integer elements due to the use of VARPTR in QBasic and QB64's emulated conventional memory.
  • BSAVE files can later be opened with BLOAD.

Example(s)

Saving array data to a file quickly.


LB% = LBOUND(Array)
bytes% = LEN(Array(LB%))
filesize& = ((UBOUND(Array) - LB%) + 1) * bytes% 
DEF SEG = VARSEG(Array(0))
BSAVE filename$, VARPTR(Array(LB%)), filesize&  ' changeable index
DEF SEG

Explanation: Procedure determines the filesize from the array size automatically. LBOUND is used with UBOUND to determine array size and byte size. Works with any type of array except variable-length strings. Used for saving program data fast.

BSAVEing a bitmap and calculating the file size


 DEF SEG = VARSEG(Image(0))
 PSET(BMPHead.PWidth - 1, BMPHead.PDepth - 1)  'color lower right corner if black
 GET (0, 0)-(BMPHead.PWidth - 1, BMPHead.PDepth - 1), Image(NColors * 3) ' for 16 or 256 colors
 FOR a& = 26000 TO 0 STEP -1
   IF Image(a&) THEN ArraySize& = a&: EXIT FOR
 NEXT
 BSAVE SaveName$, VARPTR(Image(0)), (2 * ArraySize&) + 200 'file size
 DEF SEG

Explanation: The FOR...NEXT loop reads backwards through the image array until it finds a value not 0. The LONG ArraySize& value is doubled and 200 is added. BMPhead.PWidth and BMPhead.PDepth are found by reading the bitmap's information header using a TYPE definition. See Bitmaps.

Using PUT and GET to write and read array data from a file without using BSAVE or BLOAD:


KILL "example2.BIN" 'removes old image file!

SCREEN 13
OPTION BASE 0
REDIM Graphic%(1001) 'REDIM makes array resize-able later

LINE (0, 0)-(10, 10), 12, B 'create image
GET(0, 0)-STEP(10, 10), Graphic%() 'get image to array

FOR i% = 1000 TO 0 STEP -1 'reverse read array for size needed
    IF Graphic%(i%) <> 0 THEN EXIT FOR 'find image color not black
NEXT
size% = i% + 4 'size plus 2 integers(4  bytes) for dimensions 
REDIM _PRESERVE Graphic%(size%) 'resize existing array in QB64 only!

OPEN "example2.BIN" FOR BINARY AS #1 ' PUT to a file
PUT #1, , Graphic%()
CLOSE

OPEN "example2.BIN" FOR BINARY AS #2 'GET array and PUT to screen
DIM CopyBin%(LOF(2) \ 2) 'create new array sized by half of file size
GET #2, , CopyBin%()
PUT(100, 100), CopyBin%(), PSET
fsize% = LOF(2)
CLOSE

K$ = INPUT$(1) 'Press any key 
FOR i = 0 TO 20 'read all 3 arrays
    PRINT Graphic%(i); CopyBin%(i)
NEXT
PRINT "Array:"; size%, "File:"; fsize%

Explanation: A 10 by 10 pixel box is saved to an array using the GET (graphics statement) and written to a BINARY file using PUT #1. Then GET #1 places the file contents into another INTEGER array and places it on the screen with the PUT (graphics statement).

The array contents: 88 is the width in the GET array for SCREEN 13 which needs divided by 8 in that mode only. The area is actually 11 X 11. The array size needed can be found by looping backwards through the array until a color value is found. IF array(i) <> 0 THEN EXIT FOR (66 integers) or by dividing the created BINARY file size in half (134 bytes) when known to be array sized already.

See Also