Sfumare radialmente un'immagine mediante le funzioni esterne del API di ImageMagick

Il sistema ImageMagick consente di creare, modificare e convertire immagini bitmap. Può altresì leggere e scrivere immagini di oltre 200 formati.

Per poter fruire in Gambas delle risorse, è necessario avere installata nel sistema e richiamare la seguente libreria condivisa: "libMagickWand-7.Q16HDRI.so.10.0.2 ".

Le risorse di questa libreria ci consentono - fra l'altro - di sfumare un'immagine con un effetto vortice.

Mostriamo un esempio pratico:

Library "libMagickWand-7.Q16HDRI:10.0.2"

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

' 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 MagickRadialBlurImage(MagickWand *wand, const double angle)
' Blurs an image.
Private Extern MagickRadialBlurImage(wand As MagickWand, blur As Float) 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 Main()
 
  Dim bo As Integer
  Dim mwand As MagickWand
  Dim fileimmagine, nuovofile As String

  fileimmagine = "/percorso/del/file/immagine"
  nuovofile = "/percorso/del/nuovo/file/dell'immagine/spostata"
  
  MagickWandGenesis()
     
  mwand = NewMagickWand()
  
  bo = MagickReadImage(mwand, fileimmagine)
  If bo == MagickFalse Then
    Termina(mwand)
    Error.Raise("Impossibile caricare l'immagine !")
  Endif
  
' Modifica l'immagine con l'effetto sfumato con vortice:
  MagickRadialBlurImage(mwand, 50.0)
  
  bo = MagickWriteImages(mwand, nuovofile, MagickTrue)
  If bo == MagickFalse Then
    Termina(mwand)
    Error.Raise("Impossibile creare il nuovo file dell'immagine sfumata !")
  Endif
  
  Termina(mwand)
  
End


Private Procedure Termina(mw As MagickWand)    ' Libera la memoria e termina il programma
  
  DestroyMagickWand(mw)
  Wait 0.01
  MagickWandTerminus()
  
End

Riferimenti

• https://imagemagick.org/index.php
• http://imagemagick.org/api/magick-wand.php