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Jacob Wall · (This post was last modified: 12-27-2018 09:09 PM by Jacob Wall.)

(12-27-2018 08:23 AM)Didier Lachieze Wrote: Here is how I would do it :

Code:

L0:={137,80,78}; L1:={}; N:=L0(1)*256^2+L0(2)*256+L0(3); FOR I FROM 3 DOWNTO 0 DO L1(0):=IP(N/64^I); N:=N-L1(0)*64^I; END;

L1 will return {34,21,1,14}, but you can also do the lookup and build the Base64 string directly in the loop rather than building L1.

Interesting, this makes sense. I don't work with binary enough to have figured that one out easily. I implemented this method and compared performance to original version, there is a significant improvement. Using a fairly typical screen resulting in a ~26KB file; my times were:

Previously posted version: ~14.8s
Previous version without Step 5: ~14.7s
New version using Didier's method: ~5.2s

I experimented reading 3 bytes at a time with AFilesB, but that proved to be much slower than reading in the maximum number of bytes into a local variable, then processing it 3 bytes per iteration.

Here's the latest version:

Code:

WriteBase64();

Base64String();

EXPORT base64img2()

BEGIN

  LOCAL fname:="b64img2.html",htmlcontent,fsize,fiter,cur_chunk,j;

  AFiles(fname):=G0;

  htmlcontent:="<!doctype html><html lang=\"en\"><head><meta charset=\"utf-8\"><title>Base64 Screen Capture</title></head><body><div><img style=\"display:block; margin:0 auto;\" src=\"data:image/png;base64,"+WriteBase64(fname)+"\" alt=\"Sample Screen Capture\" /></div></body></html>";

  DelAFiles(fname);

  fsize:=DIM(htmlcontent);

  IF fsize>10000 THEN // max of 10000 items in a list

    fiter:=IP(fsize/10000);

    FOR j FROM 1 TO fiter DO

      cur_chunk:=ASC(MID(htmlcontent,(j-1)*10000+1,10000));

      AFilesB(fname,(j-1)*10000):=cur_chunk;

    END;

    IF FP(fsize/10000) THEN

      cur_chunk:=ASC(MID(htmlcontent,fiter*10000+1));

      AFilesB(fname,fiter*10000):=cur_chunk;

    END;

  ELSE

    AFilesB(fname,0):=ASC(htmlcontent);

  END;

END;

WriteBase64(fname)

BEGIN

  LOCAL fcontent,j,b64str:="",fsize,fiter;

  fsize:=AFilesB(fname);

  IF fsize>9998 THEN // lists can not be longer than 10000, 9999 divides by 3 evenly

    fiter:=IP(fsize/9999);

    FOR j FROM 1 TO fiter DO

      fcontent:=AFilesB(fname,(j-1)*9999,9999);

      b64str:=b64str+Base64String(9999,fcontent);

    END;

    IF FP(fsize/9999) THEN

      fcontent:=AFilesB(fname,fiter*9999,fsize-(fiter*9999));

      b64str:=b64str+Base64String(SIZE(fcontent),fcontent);

    END;

  ELSE

    fcontent:=AFilesB(fname,0,fsize);

    b64str:=b64str+Base64String(SIZE(fcontent),fcontent);

  END;

  RETURN b64str;

END;

Base64String(fsize,mylst)

BEGIN

  LOCAL fiter:=IP(fsize/3),L1,N,j,i,mystr:="";

  LOCAL dict:={"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z","0","1","2","3","4","5","6","7","8","9","+","/"};

  FOR j FROM 1 TO fiter DO

    N:=mylst(j*3-2)*256^2+mylst(j*3-1)*256+mylst(j*3);

    FOR i FROM 3 DOWNTO 0 DO

      L1:=IP(N/64^i);

      mystr:=mystr+dict(L1+1);

      N:=N-L1*64^i;

    END;

  END;

  IF fsize-fiter*3 THEN // fractional

    IF (fsize-fiter*3)==1 THEN

      N:=mylst(fsize)*256^2;

      FOR i FROM 3 DOWNTO 2 DO

        L1:=IP(N/64^i);

        mystr:=mystr+dict(L1+1);

        N:=N-L1*64^i;

      END;

      mystr:=mystr+"==";

    ELSE // must be 2

      N:=mylst(fsize-1)*256^2+mylst(fsize)*256;

      FOR i FROM 3 DOWNTO 1 DO

        L1:=IP(N/64^i);

        mystr:=mystr+dict(L1+1);

        N:=N-L1*64^i;

      END;

      mystr:=mystr+"=";

    END;

  END;

  RETURN mystr;

END;

EDIT: Removed duplicate <body> tag