# $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 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 0 string \x00\x00\x00\x0C\x6A\x50\x20\x20\x0D\x0A\x87\x0A JPEG 2000 image data