MaplePrimes - answers and comments on Question, Is it possible to read an image from the internet into maple

Sockets

epostma — Wed, 04 Aug 2010 18:53:59 Z

Try this (with thanks to John's baby names document) :

    q := cat("GET /SizedImages/image.ashx?file=991a3b8f2151d4732c78ce6920b9dc88_60_60.jpg HTTP/1.0\n",
             "Host:    www.mapleprimes.com\n\n");
    sock := Sockets:-Open("www.mapleprimes.com", 80);
    
    Sockets:-Write(sock, q);
    
    s := Array(1..100, datatype=integer[1]);
    p := Sockets:-ReadBinary(s, sock):
    n := p;
    while p = 100 do
        a := Array(1..100, datatype=integer[1]);
        p := Sockets:-ReadBinary(a, sock):
        s(n + 1 .. n + p) := a[1 .. p];
        n := n + p;
    end do:
    
    Sockets:-Close(sock);
 
    k := 1;
    while s[k] <> 13 or s[k+1] <> 10 or s[k+2] <> 13 or s[k+3] <> 10 do
      k := k + 1;
    end do:

    s := s[k+4 ..]:

    FileTools:-Binary:-Write("file.jpg", s);
    FileTools:-Binary:-Close("file.jpg");

    img := ImageTools:-Read("file.jpg");
    ImageTools:-View(img);

Hope this helps,

Erik Postma
Maplesoft.

Could this be automated?

Robert Israel — Thu, 05 Aug 2010 04:15:35 Z

Very nice, but it would be even better if Sockets had functions that could do some of this more automatically. And it doesn't always work for me. If I try it with, say, http://www.math.ubc.ca/~israel/convhull.jpg, so the first lines are

q := cat("GET /~israel/convhull.jpg HTTP/1.0\n",
             "Host:    www.math.ubc.ca\n\n");
sock := Sockets:-Open("www.math.ubc.ca", 80);

I only get about the top half of the image.

It works well

hirnyk — Thu, 05 Aug 2010 06:41:00 Z

For me, it works well: see the output of pic.mw .

I'm getting errors

Christopher2222 — Thu, 05 Aug 2010 14:38:45 Z

Currently I'm getting these errors

    Error, index out of bounds
                                                                 true
                                                                 k:=1
    Error, Array index out of range
    Error, inverted range in Array index
                                                                  100
    Error, (in readbytes) JPEG Error: Not a JPEG file: starts with 0x48 0x54
    Error, (in ImageTools:-View) parameters must be images or lists of images

Is it supposed to work with Maple 12 ?

It works well

hirnyk — Thu, 05 Aug 2010 16:59:18 Z

For me, it works well. See a screenshot picture.doc .

The issue is the s(n+1 .. n+p) := ...

epostma — Thu, 05 Aug 2010 17:56:15 Z

@Christopher2222 : looks like extending rtables was not as powerful in Maple 12 as it is today. As a stopgap measure, you can insert the line

s(n + p) := 1;

just before the line

s(n + 1 .. n + p) := a[1 .. p];

That should extend s to the required size. I checked it in Maple 12 as well, now, and it worked for me.

Hope this helps,

Erik Postma
Maplesoft.