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# $OpenBSD: jpeg,v 1.2 2004/06/03 03:14:20 tedu Exp $
#------------------------------------------------------------------------------
# JPEG images
# SunOS 5.5.1 had
#
# 0 string \377\330\377\340 JPEG file
# 0 string \377\330\377\356 JPG file
#
# both of which turn into "JPEG image data" here.
#
0 beshort 0xffd8 JPEG image data
>6 string JFIF \b, JFIF standard
>6 string Exif \b, EXIF standard
# The following added by Erik Rossen <rossen@freesurf.ch> 1999-09-06
# in a vain attempt to add image size reporting for JFIF. Note that these
# tests are not fool-proof since some perfectly valid JPEGs are currently
# impossible to specify in magic(4) format.
# First, a little JFIF version info:
>11 byte x \b %d.
>12 byte x \b%02d
# Next, the resolution or aspect ratio of the image:
#>13 byte 0 \b, aspect ratio
#>13 byte 1 \b, resolution (DPI)
#>13 byte 2 \b, resolution (DPCM)
#>4 beshort x \b, segment length %d
# Next, show thumbnail info, if it exists:
>18 byte !0 \b, thumbnail %dx
>>19 byte x \b%d
# Here things get sticky. We can do ONE MORE marker segment with
# indirect addressing, and that's all. It would be great if we could
# do pointer arithemetic like in an assembler language. Christos?
# And if there was some sort of looping construct to do searches, plus a few
# named accumulators, it would be even more effective...
# At least we can show a comment if no other segments got inserted before:
>(4.S+5) byte 0xFE
>>(4.S+8) string >\0 \b, "%s"
#>(4.S+5) byte 0xFE \b, comment
#>>(4.S+6) beshort x \b length=%d
#>>(4.S+8) string >\0 \b, "%s"
# Or, we can show the encoding type (I've included only the three most common)
# and image dimensions if we are lucky and the SOFn (image segment) is here:
>(4.S+5) byte 0xC0 \b, baseline
>>(4.S+6) byte x \b, precision %d
>>(4.S+7) beshort x \b, %dx
>>(4.S+9) beshort x \b%d
>(4.S+5) byte 0xC1 \b, extended sequential
>>(4.S+6) byte x \b, precision %d
>>(4.S+7) beshort x \b, %dx
>>(4.S+9) beshort x \b%d
>(4.S+5) byte 0xC2 \b, progressive
>>(4.S+6) byte x \b, precision %d
>>(4.S+7) beshort x \b, %dx
>>(4.S+9) beshort x \b%d
# I've commented-out quantisation table reporting. I doubt anyone cares yet.
#>(4.S+5) byte 0xDB \b, quantisation table
#>>(4.S+6) beshort x \b length=%d
#>14 beshort x \b, %d x
#>16 beshort x \b %d
# HSI is Handmade Software's proprietary JPEG encoding scheme
0 string hsi1 JPEG image data, HSI proprietary
# From: David Santinoli <david@santinoli.com>
0 string \x00\x00\x00\x0C\x6A\x50\x20\x20\x0D\x0A\x87\x0A JPEG 2000 image data
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