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| (Una versione intermedia di uno stesso utente non è mostrata) |
| Riga 1: |
Riga 1: |
| − | Per scaricare una immagine da un sito internet e farla mostrare direttamente in una ''PictureBox'', è possibile utilizzare alcune funzioni esterne dell'API di GTK+3.
| + | #REDIRECT [[Scaricare_una_immagine_da_un_sito_internet#Usando_le_funzioni_esterne_della_libreria_libgdk_pixbuf-2.0]] |
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| − | Va sottolineato che la seguente pagina si riferisce esclusivamente ai file immagine di formato <FONT Color=#B22222>.png</font> .
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| − | E' necessario avere installata nel sistema e richiamare in Gambas la libreria dinamica condivisa: "''libgtk-3.so.0.1800.9''".
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| − | Mostriamo un esempio pratico in ambiente grafico. E' necessario attivare anche i Componenti ''gb.net'' e ''gb.net.curl''.
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| − | Private http As New HttpClient As "http"
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| − | Private loader As Pointer
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| − | Library "libgtk-3:0.1800.9"
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| − | <FONT Color=gray>' ''GdkPixbufLoader * gdk_pixbuf_loader_new(void)''
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| − | ' ''Creates a new pixbuf loader object.''</font>
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| − | Private Extern gdk_pixbuf_loader_new() As Pointer
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| − | <FONT Color=gray>' ''gboolean gdk_pixbuf_loader_write (GdkPixbufLoader *loader, const guchar *buf, gsize count, GError **error)''
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| − | ' ''Cause a pixbuf loader to parse the next count bytes of an image.''</font>
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| − | Private Extern gdk_pixbuf_loader_write(lo As Pointer, buf As Pointer, i As Integer, po As Pointer)
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| − | <FONT Color=gray>' ''gboolean gdk_pixbuf_loader_close (GdkPixbufLoader *loader, GError **error)''
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| − | ' ''Informs a pixbuf loader that no further writes.''</font>
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| − | Private Extern gdk_pixbuf_loader_close(lo As Pointer, po As Pointer)
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| − | <FONT Color=gray>' ''GdkPixbuf * gdk_pixbuf_loader_get_pixbuf (GdkPixbufLoader *loader)''
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| − | ' ''Queries the GdkPixbuf that a pixbuf loader is currently creating.''</font>
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| − | Private Extern gdk_pixbuf_loader_get_pixbuf(lo As Pointer) As Pointer
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| − | <FONT Color=gray>' ''guchar * gdk_pixbuf_get_pixels (const GdkPixbuf *pixbuf)''
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| − | ' ''Queries a pointer to the pixel data of a pixbuf.''</font>
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| − | Private Extern gdk_pixbuf_get_pixels(GdkPixbuf As Pointer) As Pointer
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| − | <FONT Color=gray>' ''int gdk_pixbuf_get_width (const GdkPixbuf *pixbuf)''
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| − | ' ''Queries the width of a pixbuf.''</font>
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| − | Private Extern gdk_pixbuf_get_width(GdkPixbuf As Pointer) As Integer
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| − | <FONT Color=gray>' ''int gdk_pixbuf_get_height (const GdkPixbuf *pixbuf)''
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| − | ' ''Queries the height of a pixbuf.''</font>
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| − | Private Extern gdk_pixbuf_get_height(GdkPixbuf As Pointer) As Integer
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| − | <FONT Color=gray>' ''int gdk_pixbuf_get_n_channels (const GdkPixbuf *pixbuf)''
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| − | ' ''Queries the number of channels of a pixbuf.''</font>
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| − | Private Extern gdk_pixbuf_get_n_channels(GdkPixbuf As Pointer) As Integer
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| − | <FONT Color=gray>' ''gboolean gdk_pixbuf_get_has_alpha (const GdkPixbuf *pixbuf)''
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| − | ' ''Queries whether a pixbuf has an alpha channel (opacity information).''</font>
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| − | Private Extern gdk_pixbuf_get_has_alpha(GdkPixbuf As Pointer) As Boolean
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| − | <FONT Color=gray>' ''void g_object_unref (gpointer object)''
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| − | ' ''Decreases the reference count of object.''</font>
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| − | Private Extern g_object_unref(_object As Pointer)
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| − | '''Public''' Sub Button1_Click()
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| − | <FONT Color=gray>' ''Invia la richiesta al server per scaricare il file immagine:''</font>
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| − | http.URL = "<FONT Color=gray>http://indirizzo/web/del/file/immagine.png''</font>"
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| − | http.Timeout = 15
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| − | http.Get()
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| − | '''End'''
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| − | '''Public''' Sub http_Finished()
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| − | Dim s As String
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| − | http.Close
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| − | s = http.Peek()
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| − | Print "Immagine scaricata !\n\nDimensione: "; Len(s); " byte"
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| − | Immagine(s)
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| − | '''End'''
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| − | '''Private''' Procedure Immagine(im As String)
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| − | Dim bb As Byte[]
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| − | Dim w, h As Integer
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| − | Dim Pixbuf, dati As Pointer
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| − | Dim c As Byte
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| − | Dim bo As Boolean
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| − | Dim st As Stream
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| − | Dim imago As Image
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| − | bb = Byte[].FromString(im)
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| − | loader = gdk_pixbuf_loader_new()
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| − | gdk_pixbuf_loader_write(loader, bb.data, bb.count, 0)
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| − | gdk_pixbuf_loader_close(loader, 0)
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| − | pixbuf = gdk_pixbuf_loader_get_pixbuf(loader)
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| − | w = gdk_pixbuf_get_width(Pixbuf)
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| − | Print "Larghezza: "; w; " pixel"
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| − | h = gdk_pixbuf_get_height(Pixbuf)
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| − | Print "Altezza: "; h; " pixel"
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| − | c = gdk_pixbuf_get_n_channels(Pixbuf)
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| − | Print "Canali: "; c
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| − | bo = gdk_pixbuf_get_has_alpha(Pixbuf)
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| − | If bo = False Then Error.Raise("L'immagine scaricata è priva del canale Alfa !")
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| − | dati = gdk_pixbuf_get_pixels(Pixbuf)
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| − | If IsNull(dati) Then Error.Raise("Impossibile ottenere un 'Puntatore' ai dati dei pixel dell'immagine !")
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| − | <FONT Color=gray>' ''Carichiamo i dati nel vettore "bb[]" per gestire successivamente i dati grezzi dei pixel:''</font>
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| − | st = Memory dati For Read
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| − | bb = New Byte[w * h * c]
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| − | bb.Read(st, 0, bb.count)
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| − | st.Close
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| − | <FONT Color=gray>' ''Viene preparata la variabile di tipo immagine per la gestione dei dati del futuro nuovo file immagine:''</font>
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| − | With imago = New Image(w, h, 0, 0)
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| − | st = Memory .Data For Write
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| − | End With
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| − | <FONT Color=gray>' ''Scrive i dati presenti nel vettore "bb[]" nella varibile di tipo "Image":''</font>
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| − | bb.Write(st, 0, bb.Count)
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| − | st.Close
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| − | With PictureBox1
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| − | .W = w
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| − | .H = h
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| − | .Picture = imago.Picture
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| − | End With
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| − | '''End'''
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| − | '''Public''' Sub Form_Close()
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| − | Chiude()
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| − | '''End'''
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| − | '''Private''' Procedure Chiude()
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| − | g_object_unref(loader)
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| − | Me.Close
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| − | '''End'''
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