Re: gdk_draw_gray_image.

[Patrice St-Gelais <patrice st-gelais oricom ca>]

Hi,

I don't think your can write directly into a GdkWindow.

I coded something similar some time ago.  I wrote the data in a GdkPixmap *,
which was created with

 gdk_pixmap_new (image_area->window,
                image_area->allocation.width,
                image_area->allocation.height, -1);

... in a "configure_event" connected to "image_area".  "image_area" is created
with gtk_image_area_new();

Here is the example, if it can help - it was intended to draw continuously a
scanned image coming from a "popened" FILE *:

typedef struct {
 guchar *image_buf;
 gint image_depth; /* 1, 8, 24 bits */
 gint x;
 gint y;
} rgbbuftype;

void read_image_in_pixmap(FILE *pipeline, rgbbuftype *rgbbuf,
  GtkWidget *image_area, int ifdisplay, GdkPixmap *pixmap)
{
 // Draws continuously the image in the backup pixmap,line by line
 int i,j,k,x,y,linesize,charread;
 char c;
 // We round linesize for bitmaps
 linesize = (int) (rgbbuf->x+(rgbbuf->image_depth==1?7:0))  *
rgbbuf->image_depth / 8;
 for (y=0; y<rgbbuf->y; y++) {
  switch (rgbbuf->image_depth) {
  case 1:
   k=0;
   for (i=0; i < linesize; i++) {
    c = fgetc(pipeline);
    // Expand each bit - image_buf is initialised with 0x00's
    for (j=0; j<8 ; j++) {
     if (! (c & (guchar) (0x80 >> j)))
      *(rgbbuf->image_buf+(y*rgbbuf->x)+k) = '\377';
     if (k++ == rgbbuf->x) break;
    }
   }
   if (ifdisplay)
    gdk_draw_gray_image(pixmap, image_area->style->black_gc,
    0, y, rgbbuf->x, 1, GDK_RGB_DITHER_NONE,
    rgbbuf->image_buf+(y*rgbbuf->x), rgbbuf->x);
   break;
  case 8 :
   charread=fread(rgbbuf->image_buf+(y*linesize),1,linesize,pipeline);
   if (ifdisplay)
    gdk_draw_gray_image(pixmap, image_area->style->black_gc,
    0, y, rgbbuf->x, 1, GDK_RGB_DITHER_NONE,
    rgbbuf->image_buf+(y*linesize), linesize);
   break;
  case 24 :
   charread=fread(rgbbuf->image_buf+(y*linesize),1,linesize,pipeline);
   if (ifdisplay)
    gdk_draw_rgb_image(pixmap, image_area->style->black_gc,
    0, y, rgbbuf->x, 1, GDK_RGB_DITHER_NONE,
    rgbbuf->image_buf+(y*linesize), linesize);
  } // switch
  if (ifdisplay) Repaint(0,y,rgbbuf->x,1);
 } // for
 if (ifdisplay) {
  draw_selection(pixmap, invert_gc);
  Repaint(0,0,image_area->allocation.width,image_area->allocation.height);
 }
 return;
}

Regards,

Patrice St-Gelais
_____________________________________

"Klein, Lisa L." a écrit :

> I am attempting to draw an image line-by-line from data received one row at
> a time. Currently, I am reading the data from a file, one line at a time,
> and I either get an empty window that hangs, or a "BadMatch (invalid
> parameter attributes)" error: "serial 119  error_code 8  request _code 72
> minor_code 0". I know that the error has something to do with the
> combination of the imagewidth, imageheight, and stride parameters to
> gdk_draw_gray_image(). I used GLADE to create a window and a drawing_area
> with an expose_event signal callback (code follows).
>
> gboolean on_drawingarea1_expose_event (GtkWidget *widget, GdkEventExpose
> *event, gpointer user_data)
> {
>   FILE *fd;
>   int count=0, i;
>   unsigned char inbuf[43];
>   guchar *pixbuf;
>
>   /* Data file which is 43 columns wide and very long */
>   fd = fopen("datafile.dat", "r");
>   /* Read fifty lines of data from file as a test */
>   for(i=0; i<50; i++)
>   {
>     /* Each element in file is an 8-bit grayscale value */
>     count = fread(inbuf, sizeof(unsigned char), 43, fd);
>     pixbuf = inbuf;
>     gdk_draw_gray_image(widget->window,
> widget->style->fg_gc[GTK_STATE_NORMAL],
>                                       0, i, 43, 1,GDK_RGB_DITHER_NORMAL,
> pixbuf, 43);
>   }
>
>   return FALSE;
>
> }
>
> I think the problem might be that the function is meant to draw an entire
> image at once and fill the drawable space. I have exhausted my resources, so
> any insight anyone might provide would be helpful. Thanks.
>
> Lisa
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