Here's another attempt. -- Richard
Index: jpeg-8d/jpegtran.1 =================================================================== --- jpeg-8d.orig/jpegtran.1 2009-12-28 13:38:22.000000000 -0600 +++ jpeg-8d/jpegtran.1 2013-06-24 18:04:21.955482327 -0500 @@ -19,6 +19,10 @@ for example from baseline JPEG to progre perform some rearrangements of the image data, for example turning an image from landscape to portrait format by rotation. .PP +Modern JPEG files often contain Exif data; for such files, you may prefer +.B exiftran +instead. +.PP .B jpegtran works by rearranging the compressed data (DCT coefficients), without ever fully decoding the image. Therefore, its transformations are lossless: @@ -28,7 +32,10 @@ followed by .B cjpeg to accomplish the same conversion. But by the same token, .B jpegtran -cannot perform lossy operations such as changing the image quality. +cannot perform lossy operations such as changing the image quality. However, +while the image data is losslessly transformed, metadata can be lost. See the +.B \-copy +option for specifics. .PP .B jpegtran reads the named JPEG/JFIF file, or the standard input if no file is @@ -198,16 +205,17 @@ such as comment blocks: .TP .B \-copy none Copy no extra markers from source file. This setting suppresses all -comments and other excess baggage present in the source file. +comments and other metadata in the source file. .TP .B \-copy comments Copy only comment markers. This setting copies comments from the source file, -but discards any other inessential (for image display) data. +but discards any other metadata. .TP .B \-copy all -Copy all extra markers. This setting preserves miscellaneous markers +Copy all extra markers. This setting preserves metadata found in the source file, such as JFIF thumbnails, Exif data, and Photoshop -settings. In some files these extra markers can be sizable. +settings. In some files these extra markers can be sizable. Note that this +option will copy thumbnails as-is; they will not be transformed. .IP The default behavior is .BR "\-copy comments" .
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