Versione delle 18:15, 25 dic 2019

GTK+3 è una libreria per la creazione di interfacce grafiche utente. GDK-PixBuf è una libreria grafica per il caricamento e la manipolazione delle immagini.

Fra molteplici potenzialità esse consentono di ottenere alcune informazioni sui file immagine.

Sarà necessario avere installata nel sistema la libreria: "libgtk-3.so.0.2200.30".

Mostriamo un semplice esempio pratico:

Public Struct GdkPixbufFormat
  name As Pointer
  signature As Pointer
  domain As Pointer
  description As Pointer
  mime_types As Pointer
  extensions As Pointer
  flags As Integer
  disabled As Boolean
  license As Pointer
End Struct

Library "libgtk-3:0.2200.30"

' GdkPixbuf * gdk_pixbuf_new_from_file (const char *filename, GError **error)
' Creates a new pixbuf by loading an image from a file.
Private Extern gdk_pixbuf_new_from_file(filename As String, GError As Pointer) As Pointer

' guchar * gdk_pixbuf_get_pixels (const GdkPixbuf *pixbuf)
' Queries a pointer to the pixel data of a pixbuf.
Private Extern gdk_pixbuf_get_pixels(GdkPixbuf As Pointer) As Pointer

' int gdk_pixbuf_get_width (const GdkPixbuf *pixbuf)
' Queries the width of a pixbuf.
Private Extern gdk_pixbuf_get_width(GdkPixbuf As Pointer) As Integer

' int gdk_pixbuf_get_height (const GdkPixbuf *pixbuf)
' Queries the height of a pixbuf.
Private Extern gdk_pixbuf_get_height(GdkPixbuf As Pointer) As Integer

' int gdk_pixbuf_get_n_channels (const GdkPixbuf *pixbuf)
' Queries the number of channels of a pixbuf.
Private Extern gdk_pixbuf_get_n_channels(GdkPixbuf As Pointer) As Integer

' gboolean gdk_pixbuf_get_has_alpha (const GdkPixbuf *pixbuf)
' Queries whether a pixbuf has an alpha channel (opacity information).
Private Extern gdk_pixbuf_get_has_alpha(GdkPixbuf As Pointer) As Boolean

' GdkPixbufFormat * gdk_pixbuf_get_file_info (const gchar *filename, gint *width, gint *height)
' Parses an image file far enough to determine its format and size.
Private Extern gdk_pixbuf_get_file_info(filename As String, width As Pointer, height As Pointer) As Pointer


Public Sub Main()

 Dim nomefile As String = "/percorso/del/file/immagine"
 Dim w, wi, h, hi As Integer
 Dim Pixbuf As Pointer
 Dim c As Byte
 Dim bo As Boolean
 Dim PixbufFormat As New GdkPixbufFormat

  Pixbuf = gdk_pixbuf_new_from_file(nomefile, 0)

  w = gdk_pixbuf_get_width(Pixbuf)
  Print "Larghezza: "; Null, w; " pixel"
  h = gdk_pixbuf_get_height(Pixbuf)
  Print "Altezza: "; Null, h; " pixel"
  c = gdk_pixbuf_get_n_channels(Pixbuf)
  Print "Canali: "; Null, c
  bo = gdk_pixbuf_get_has_alpha(Pixbuf)
  Print "Canale Alfa: "; Null, bo

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''

  PixbufFormat = gdk_pixbuf_get_file_info(nomefile, VarPtr(wi), VarPtr(hi))
  Print "\nLarghezza: "; Null, wi; " pixel"
  Print "Altezza: "; Null, hi; " pixel"

  With PixbufFormat
    Print "Name:        "; String@(.name)                  ' Il nome del formato immagine
    Print "Domain:      "; String@(.domain)                ' Il contrassegno del modulo
    Print "Description: "; String@(.description)           ' Il dominio del messaggio per la descrizione
    Print "Mime-Type:   "; String@(Pointer@(.mime_types))  ' Una descrizione del formato immagine
    Print "Extension:   "; String@(Pointer@(.extensions))  ' Un array di MIME-types del formato immagine
    Print "Flag:        ".flags               ' Combinazione di flags che specifica ulteriori dettagli sulle operazioni supportate
    Print "License: "; String@(.license)      ' Informazione sulla licenza relativa al formato immagine
  End With

End

Riferimenti

• GTK+ 3 Reference Manual
• GDK-PixBuf Reference Manual