Declare Function BLoad ( ByRef filename As Const String, ByVal dest As Any Ptr = 0, ByVal pal As Any Ptr = 0 ) As Long

result = BLoad( filename [, [ dest ] [, pal ] ] )

filename
dest
pal

Returns zero (0) if successful, or a non-zero error code to indicate a failure. (throws a runtime error)

BLoad can be used to load image data or any other data from a file created with BSave, and store that data in an array or paste it to the screen. If dest is absent or null (0), the image data is pasted to the current graphics screen work page. Otherwise it is loaded as image data to the address given by dest.
BLoad must be called only if a graphics mode is initialized, else the program crashes (see BLOAD/BSAVE text mode work-around to work in text mode).

BLoad can load 4 different types of files:

• Old QB-like data files, saved with BSAVE from QB code, containing "raw" data preceded by a 7-byte header, beginning with &HFD, up to 64 KiB in size
  
• New FB-like data files, saved with BSave from FB code, containing "raw" data preceded by a 5-byte header, beginning with &HFE. There is no 64 KiB limit with this format
  
• BMP image files, supports a subset of valid ("Windows") .BMP files, beginning with "BM", saved from FB code with BSave, or created / saved in a compatible format using a graphics editor / converter.
  
• PNG image files, beginning with the standard PNG signature, saved from FB code with BSave or created by a compatible graphics editor / converter.
  

QB-like data files, BMP files, and PNG files are converted to an FB-compatible image format when opened.

Image files with 8-bit per pixel resolution or lower contain a palette that describes the color values used in the images. If pal is not null (0), the palette is copied to memory starting at the address specified. Otherwise, if the current graphics screen uses a palette then its palette is changed to match that of the image file.

When using one of the 2 raw-data file formats to save images, the image files must have been created with BSave in the same graphics screen mode as it is being loaded into. This restriction does not apply to BMP or PNG files.

When loading a BMP file using BLoad, the images must be true-color (15-, 16-, 24- or 32-bits per pixel) or palettized/indexed (8-bit or lower). The image data will be converted to the proper pixel format for the current color depth, except that true-color can't be reduced to a palettized image. BLoad doesn't support BMP files using RLE compression. BLoad will load alpha channel information, if available, from 32-bit BMP files with BITMAPV4HEADER or BITMAPV5HEADER file headers.

PNG input may be indexed, grayscale, grayscale with alpha, true-color, or true-color with alpha. Standard 1-, 2-, 4-, 8-, and 16-bit sample depths are accepted where the PNG format permits them. Scanline filters and Adam7 interlacing are supported. Alpha and tRNS transparency are retained when loading into a 32-bit target. As with BMP input, true-color PNG data can't be reduced to a palettized target.

The error code returned by BLoad can be checked using Err in the next line. The function version of BLoad returns directly the error code as a 32 bit Long.

Runtime errors:
BLoad throws one of the following runtime errors:

• dest was not specified or was null (0), and no graphics screen was set.
  
• The Bitmap uses an unsupported BMP file compression type (BI_RLE4, BI_RLE8)
  
• The Bitmap is true-color (16, 24, or 32 bits per pixel) and the current graphics screen uses a palette (8 bits per pixel or lower).
  

• The file filename could not be found.
  

• The file doesn't have any of the supported types
  
• A general read error occurred.
  

Note: When you use BLoad to load a BMP or PNG file into an image buffer, the original dimensions of the image buffer are not changed. If you want the image buffer to have the same dimensions as the file, find the dimensions beforehand and create an image of the right size. See the BMP example below for an example.

'Load a graphic to current work page
Screen 18, 32
Cls
BLoad "picture.bmp"
Sleep

'Load a 48x48 bitmap into an image
ScreenRes 320, 200, 32
Dim myImage As Any Ptr = ImageCreate( 48, 48 )
BLoad "picture.bmp", myImage
Put (10,10), myImage
ImageDestroy( myImage )
Sleep

ScreenRes 640, 480, 8 '' 8-bit palette graphics mode
Dim pal(0 To 256-1) As Integer '' 32-bit integer array with room for 256 colors

'' load bitmap to screen, put palette into pal() array
BLoad "picture.bmp", , @pal(0)

WindowTitle "Old palette"
Sleep

'' set new palette from pal() array
Palette Using pal(0)

WindowTitle "New palette"
Sleep

'' A function that creates an image buffer with the same 
'' dimensions as a BMP image, and loads a file into it.

Const NULL As Any Ptr = 0

Function bmp_load( ByRef filename As Const String ) As Any Ptr

    Dim As Long filenum, bmpwidth, bmpheight
    Dim As Any Ptr img

    '' open BMP file
    filenum = FreeFile()
    If Open( filename For Binary Access Read As #filenum ) <> 0 Then Return NULL

        '' retrieve BMP dimensions
        Get #filenum, 19, bmpwidth
        Get #filenum, 23, bmpheight

    Close #filenum

    '' create image with BMP dimensions
    img = ImageCreate( bmpwidth, Abs(bmpheight) )

    If img = NULL Then Return NULL

    '' load BMP file into image buffer
    If BLoad( filename, img ) <> 0 Then ImageDestroy( img ): Return NULL

    Return img

End Function



Dim As Any Ptr img

ScreenRes 640, 480, 32

img = bmp_load( "picture.bmp" )

If img = NULL Then
    Print "bmp_load failed"

Else

    Put (10, 10), img

    ImageDestroy( img )

End If

Sleep

• Support for loading BMP files is new to FreeBASIC.
  
• Support for loading PNG files is new to FreeBASIC.
  
• Support for retrieving the palette from BMP files is new to FreeBASIC.
  
• FreeBASIC uses a different file format from QBASIC internally, which doesn't have the 64 KiB limit, and is unsupported by QBASIC.
  
  

• BSave
  
• Palette
  
• ImageCreate
  
• ImageDestroy
  
• Internal Graphics Formats