Method Image.GIF.render_block()

Method render_block

string render_block(object img, object colortable, int x, int y, int localpalette)
string render_block(object img, object colortable, int x, int y, int localpalette, object alpha)
string render_block(object img, object colortable, int x, int y, int localpalette, object alpha, int r, int g, int b)
string render_block(object img, object colortable, int x, int y, int localpalette, int delay, int transp_index, int interlace, int user_input, int disposal)
string render_block(object img, object colortable, int x, int y, int localpalette, object alpha, int r, int g, int b, int delay, int interlace, int user_input, int disposal)

Description

This function gives a image block for placement in a GIF file, with or without transparency. The some options actually gives two blocks, the first with graphic control extensions for such things as delay or transparency.

Example:

img1=Image.Image ([...]);
img2=Image.Image ([...]);
[...] // make your very-nice images
nct=Image.Colortable ([...]); // make a nice colortable
write(Image.GIF.header_block (xsize,ysize,nct)); // write a GIF header
write(Image.GIF.render_block (img1,nct,0,0,0,10)); // write a render block
write(Image.GIF.render_block (img2,nct,0,0,0,10)); // write a render block
[...]
write(Image.GIF.end_block ()); // write end block
// voila! A GIF animation on stdout.

The above animation is thus created:

object nct=Image.Colortable(lena,32,({({0,0,0})}));
string s=GIF.header_block(lena->xsize(),lena->ysize(),nct);
foreach ( ({lena->xsize(),
            (int)(lena->xsize()*0.75),
            (int)(lena->xsize()*0.5),
            (int)(lena->xsize()*0.25),
            (int)(1),
            (int)(lena->xsize()*0.25),
            (int)(lena->xsize()*0.5),
            (int)(lena->xsize()*0.75)}),int xsize)
{
   object o=lena->scale(xsize,lena->ysize());
   object p=lena->clear(0,0,0);
   p->paste(o,(lena->xsize()-o->xsize())/2,0);
   s+=Image.GIF.render_block(p,nct,0,0,0,25);
}
s+=Image.GIF.netscape_loop_block(200);
s+=Image.GIF.end_block();
write(s);

Parameter img

The image.

Parameter colortable

Colortable with colors to use and to write as palette.

Parameter x

Parameter y

Position of this image.

Parameter localpalette

If set, writes a local palette.

Parameter alpha

Alpha channel image; black is transparent.

Parameter r

Parameter g

Parameter b

Color of transparent pixels. Not all decoders understands transparency. This is ignored if localpalette isn't set.

Parameter delay

View this image for this many centiseconds. Default is zero.

Parameter transp_index

Index of the transparent color in the colortable. -1 indicates no transparency.

Parameter user_input

If set: wait the delay or until user input. If delay is zero, wait indefinitely for user input. May sound the bell upon decoding. Default is non-set.

Parameter disposal

Disposal method number;

Note

This is in the advanced sector of the GIF support; please read some about how GIFs are packed.

The user_input and disposal method are unsupported in most decoders.

See also

encode , header_block , end_block