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- #------------------------------------------------------------------------------
- # 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
- # 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)
- >14 beshort x \b X%d:
- >16 beshort x \bY%d
- #>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
- # HSI is Handmade Software's proprietary JPEG encoding scheme
- 0 string hsi1 JPEG image data, HSI proprietary
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