Visualizza wikitesto di Convertire un file immagine in un altro formato immagine con le funzioni esterne del API di ImageMagick

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. <SUP>&#091;[[#Note|nota 1]]&#093;</sup>

Sarà necessario avere installata nel proprio sistema la libreria condivisa: "''libMagickWand-7.Q16HDRI.so.10.0.1'' ".

Mostriamo un esempio pratico, con il quale si convertirà un file immagine in un file immagine di formato WEBP:
 Library "libMagickWand-7.Q16HDRI:10.0.1"
 
 Private Const MagickPathExtent As Integer = 4096
 
 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
 
 <FONT Color=gray>' ''void MagickWandGenesis(void)''
 ' ''Initializes the MagickWand environment.''</font>
 Private Extern MagickWandGenesis()
 
 <FONT Color=gray>' ''MagickWand *NewMagickWand(void)''
 ' Returns a wand required for all other methods in the API.''</font>
 Private Extern NewMagickWand() As MagickWand
 
 <FONT Color=gray>' ''MagickBooleanType MagickReadImage(MagickWand *wand,const char *filename)''
 ' ''Reads an image or image sequence.''</font>
 Private Extern MagickReadImage(wand As MagickWand, filename As String) As Integer
 
 <FONT Color=gray>' ''MagickBooleanType MagickWriteImages(MagickWand *wand, const char *filename,const MagickBooleanType adjoin)''
 ' ''Writes an image or image sequence.''</font>
 Private Extern MagickWriteImages(wand As MagickWand, filename As String, adjoin As Boolean) As Integer
 
 <FONT Color=gray>' ''MagickWand *DestroyMagickWand(MagickWand *wand)''
 ' ''Deallocates memory associated with an MagickWand.''</font>
 Private Extern DestroyMagickWand(wand As MagickWand) As MagickWand
 
 <FONT Color=gray>' ''void MagickWandTerminus(void)''
 ' ''Terminates the MagickWand environment.''</font>
 Private Extern MagickWandTerminus()
 
 
 Public Sub Form_Open()
 
  Dim bo As Integer
  Dim mwand As MagickWand
  Dim fileimmagine, nuovofile As String
 
  fileimmagine = "<FONT Color=darkgreen>''/percorso/del/file/da/convertire''</font>"
  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)    <FONT Color=gray>' ''Libera la memoria e termina il programma''</font>
 
  DestroyMagickWand(mw)
  MagickWandTerminus()
 
 End



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