Ottenere alcune informazioni sul file immagine con le funzioni del API di GTK+3 e GDK-PixBuf
Da Gambas-it.org - Wikipedia.
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: "libgdk_pixbuf-2.0.so.0.4200.8 ".
Mostriamo un semplice esempio pratico:
Library "libgdk_pixbuf-2.0:0.4200.8"
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
' 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
' int gdk_pixbuf_get_bits_per_sample (const GdkPixbuf *pixbuf)
' Queries the number of bits per color sample in a pixbuf.
Private Extern gdk_pixbuf_get_bits_per_sample(pixbuf As Pointer) As Integer
' int gdk_pixbuf_get_rowstride (const GdkPixbuf *pixbuf)
' Queries the rowstride of a pixbuf.
Private Extern gdk_pixbuf_get_rowstride(pixbuf As Pointer) As Integer
' gsize gdk_pixbuf_get_byte_length (const GdkPixbuf *pixbuf)
' Returns the length of the pixel data, in bytes.
Private Extern gdk_pixbuf_get_byte_length(pixbuf As Pointer) As Long
' 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
' void g_object_unref (gpointer object)
' Decreases the reference count of object.
Private Extern g_object_unref(gobject As Pointer)
Public Sub Main()
Dim nomefile As String = "/percorso/del/file/immagine"
Dim i, wi, hi As Integer
Dim l As Long
Dim pixbuf As Pointer
Dim bo As Boolean
Dim PixbufFormat As New GdkPixbufFormat
pixbuf = gdk_pixbuf_new_from_file(nomefile, 0)
If pixbuf == 0 Then Error.Raise("Errore !")
Print "File immagine: "; nomefile
i = gdk_pixbuf_get_width(pixbuf)
Print "Larghezza: "; i; " pixel"
i = gdk_pixbuf_get_height(pixbuf)
Print "Altezza: "; i; " pixel"
i = gdk_pixbuf_get_rowstride(pixbuf)
Print "Numero di byte per riga: "; i
i = gdk_pixbuf_get_n_channels(pixbuf)
Print "Canali: "; i
bo = gdk_pixbuf_get_has_alpha(pixbuf)
Print "Canale Alfa: "; bo
i = gdk_pixbuf_get_bits_per_sample(pixbuf)
Print "Risoluzione: "; i; " bit"
l = gdk_pixbuf_get_byte_length(pixbuf)
Print "Lunghezza dei dati pixel: "; l; " byte"
g_object_unref(pixbuf)
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''
PixbufFormat = gdk_pixbuf_get_file_info(nomefile, VarPtr(wi), VarPtr(hi))
With PixbufFormat
Print "\nName: "; 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
