Versione delle 15:02, 30 set 2023

Le risorse della libreria esterna ImageMagick consentono di convertire un file immagine in uno di questi formati: PNG, JPEG, BMP, TIFF, WebP, GIF e TGA. ^{[nota 1]}

Sarà necessario avere installata nel proprio sistema l libreri CONDIVISA: "libMagickWand-6.Q16.SO.6.0.0 ".

Mostriamo un esempio pratico, con il quale si convertirà un file immagine in un file immagine di formato WEBP:

Library "libMagickWand-6.Q16:6.0.0"

Public Struct MagickWand
  id As Long
  name[MagickPathExtent] As Byte
  images As Pointer
  image_info As Pointer
  exception As Pointer
  insert_before As Integer
  image_pending As Integer
  debug_ As Integer
  signature As Long
End Struct

Private Enum MagickFalse = 0, MagickTrue
Private Const MagickPathExtent As Integer = 4096

' void MagickWandGenesis(void)
' Initializes the MagickWand environment.
Private Extern MagickWandGenesis()

' MagickWand *NewMagickWand(void)
' Returns a wand required for all other methods in the API.
Private Extern NewMagickWand() As MagickWand

' MagickBooleanType MagickReadImage(MagickWand *wand,const char *filename)
' Reads an image or image sequence.
Private Extern MagickReadImage(wand As MagickWand, filename As String) As Integer

' MagickBooleanType MagickWriteImages(MagickWand *wand, const char *filename,const MagickBooleanType adjoin)
' Writes an image or image sequence.
Private Extern MagickWriteImages(wand As MagickWand, filename As String, adjoin As Boolean) As Integer

' MagickWand *DestroyMagickWand(MagickWand *wand)
' Deallocates memory associated with an MagickWand.
Private Extern DestroyMagickWand(wand As MagickWand) As MagickWand

' void MagickWandTerminus(void)
' Terminates the MagickWand environment.
Private Extern MagickWandTerminus()


Public Sub Form_Open()

 Dim bo As Integer
 Dim mwand As MagickWand
 Dim fileimmagine, nuovofile As String

 fileimmagine = "/percorso/del/file/da/convertire"
 nuovofile = "/tmp/immagine.webp"

 MagickWandGenesis()

 mwand = NewMagickWand()

 bo = MagickReadImage(mwand, fileimmagine)
 If bo = MagickFalse Then
   Termina(mwand)
   Error.Raise("Impossibile caricare l'immagine !")
 Endif

 bo = MagickWriteImages(mwand, nuovofile, MagickTrue)
 If bo = MagickFalse Then
   Termina(mwand)
   Error.Raise("Impossibile creare il nuovo file dell'immagine ruotata !")
 Endif

 Termina(mwand)

End


Private Procedure Termina(mw As MagickWand)    ' Libera la memoria e termina il programma

 DestroyMagickWand(mw)
 MagickWandTerminus()

End

Note

[1] Vedere questa pagina: https://products.fileformat.com/image/c/imagemagick/