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Diffstat (limited to 'contrib/file/Magdir/jpeg')
| -rw-r--r-- | contrib/file/Magdir/jpeg | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/contrib/file/Magdir/jpeg b/contrib/file/Magdir/jpeg new file mode 100644 index 0000000..089405a --- /dev/null +++ b/contrib/file/Magdir/jpeg @@ -0,0 +1,61 @@ + +#------------------------------------------------------------------------------ +# 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 |
