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david van brink // Thu 2007.11.15 22:07 // {after effects extendscript}

Binary Files in ExtendScript

Adobe’s done a real whiz-bang job with their scripting support, known as ExtendScript. They’ve filled in some important missing pieces to make JavaScript into a full-featured programming environment, include network communications, XML, and graphic UI elements. These are uniformly available across all their scriptable applications (with, alas, minor variations with the UI support).

This post shows a little example of how to use the humble File object.

Like all good library writers, they’ve designed File to shield us from the absolute blazing stupidity of different linefeed characters. It detects CR, LF, LFCR, and CRLF and still chugs along reading your files, line by line, correctly. No, really, it does work!

So the exciting case of course is, how to defeat that and read or write binary files? This example demonstrates the recipe.


// adobe extendscript writing binary data
var f = new File("/Users/poly/junk/jsbinTest.bin");
f.encoding = "BINARY";

f.open ("w");

for(i = 0; i < 256; i++)
	f.write(String.fromCharCode (i));

f.write("this file is: " + f.fsName + "\n");

f.close();

They've got this highly-developed notion of "encoding", but, in truth, you can usually either ignore it, for text, or set it to the magic value BINARY. Easy peasy!

Note also the standard JavaScript String.fromCharCode(integer).

And here's the file created by that ExtendScript code snippet.

poly@Omino-Lux: hexdump -C ~/junk/jsbinTest.bin 
00000000  00 01 02 03 04 05 06 07  08 09 0a 0b 0c 0d 0e 0f  |................|
00000010  10 11 12 13 14 15 16 17  18 19 1a 1b 1c 1d 1e 1f  |................|
00000020  20 21 22 23 24 25 26 27  28 29 2a 2b 2c 2d 2e 2f  | !"#$%&'()*+,-./|
00000030  30 31 32 33 34 35 36 37  38 39 3a 3b 3c 3d 3e 3f  |0123456789:;<=>?|
00000040  40 41 42 43 44 45 46 47  48 49 4a 4b 4c 4d 4e 4f  |@ABCDEFGHIJKLMNO|
00000050  50 51 52 53 54 55 56 57  58 59 5a 5b 5c 5d 5e 5f  |PQRSTUVWXYZ[\]^_|
00000060  60 61 62 63 64 65 66 67  68 69 6a 6b 6c 6d 6e 6f  |`abcdefghijklmno|
00000070  70 71 72 73 74 75 76 77  78 79 7a 7b 7c 7d 7e 7f  |pqrstuvwxyz{|}~.|
00000080  80 81 82 83 84 85 86 87  88 89 8a 8b 8c 8d 8e 8f  |................|
00000090  90 91 92 93 94 95 96 97  98 99 9a 9b 9c 9d 9e 9f  |................|
000000a0  a0 a1 a2 a3 a4 a5 a6 a7  a8 a9 aa ab ac ad ae af  |................|
000000b0  b0 b1 b2 b3 b4 b5 b6 b7  b8 b9 ba bb bc bd be bf  |................|
000000c0  c0 c1 c2 c3 c4 c5 c6 c7  c8 c9 ca cb cc cd ce cf  |................|
000000d0  d0 d1 d2 d3 d4 d5 d6 d7  d8 d9 da db dc dd de df  |................|
000000e0  e0 e1 e2 e3 e4 e5 e6 e7  e8 e9 ea eb ec ed ee ef  |................|
000000f0  f0 f1 f2 f3 f4 f5 f6 f7  f8 f9 fa fb fc fd fe ff  |................|
00000100  74 68 69 73 20 66 69 6c  65 20 69 73 3a 20 2f 55  |this file is: /U|
00000110  73 65 72 73 2f 70 6f 6c  79 2f 6a 75 6e 6b 2f 6a  |sers/poly/junk/j|
00000120  73 62 69 6e 54 65 73 74  2e 62 69 6e 0a           |sbinTest.bin.|

So why interact with binary files and, oh, say, After Effects? I have some ideas...

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