I tried to use convert of imagemagick 6.5.6 to make a smaller version from original JPEG file in both file size and geometry. The command I used is:
convert tj/p1.jpg -resize 500x tj/456c2e75fe0faa57fd1cfd87117e0963/p1.jpg
The result is funny, the original is 1102x1542+0+0 in 164kb, the converted one is 500x700+0+0 in 174kb. The pixel count is almost the 20% of the original version, with much bigger file size. So I add -strip options to remove all the verbose info开发者_如何学运维rmation in JPEG profile.
convert tj/p1.jpg -strip -resize 500x tj/500_p1.jpg
The 500_p1.jpg is 500x700+0+0 in 173kb, only 1kb less.
Also I tried to use -thumbnail for it.
convert tj/p1.jpg -thumbnail 500x tj/th/p1.jpg
The thumbed jpeg is 500x700+0+0 in 173kb as well.
Finally I found the -quality can help to reduce images. But 75% quality takes 107kb, 25% quality takes only 50kb with visible loss of detail. But the original quality factor is unknown.
Does anyone have similar issues? Hereafter are the image profiles generated by identify. I found the major differences as following:
Geometry: 1102x1542->500x700 print size: 11x15->5x7 Units: Undefined->PixelsPerInch Quality: unknown->92 Nr. of Pixels: 1.621mb->342kb
Detail of profiles:
Original:
Image: tj/p1.jpg Format: JPEG (Joint Photographic Experts Group JFIF format) Class: DirectClass Geometry: 1102x1542+0+0 Resolution: 100x100 Print size: 11.02x15.42 Units: Undefined Type: TrueColor Endianess: Undefined Colorspace: RGB Depth: 8-bit Channel depth: red: 8-bit green: 8-bit blue: 8-bit Channel statistics: red: min: 0 (0) max: 255 (1) mean: 218.106 (0.855319) standard deviation: 52.7336 (0.206798) kurtosis: 5.04278 skewness: -2.24455 green: min: 0 (0) max: 255 (1) mean: 158.476 (0.621473) standard deviation: 92.9844 (0.364645) kurtosis: -1.24112 skewness: -0.535292 blue: min: 0 (0) max: 255 (1) mean: 113.282 (0.444244) standard deviation: 99.7003 (0.390981) kurtosis: -1.59582 skewness: 0.278377 Image statistics: Overall: min: 0 (0) max: 255 (1) mean: 122.466 (0.480259) standard deviation: 108.274 (0.424604) kurtosis: -1.78198 skewness: 0.0115088 Rendering intent: Undefined Interlace: None Background color: white Border color: rgb(223,223,223) Matte color: grey74 Transparent color: black Page geometry: 1102x1542+0+0 Dispose: Undefined Iterations: 0 Compression: JPEG Orientation: Undefined Properties: date:create: 2010-10-22T08:35:35+08:00 date:modify: 2010-09-30T10:52:06+08:00 jpeg:colorspace: 2 jpeg:sampling-factor: 2x2,1x1,1x1 signature: cdbd3f63986f0a7c4cd20aedcf9123d91df97e0cb7388f59059b4676fd36d481 Profiles: Profile-APP12: 15 bytes Artifacts: verbose: true Tainted: False Filesize: 164kb Number pixels: 1.621mb Pixels per second: 20.51mb User time: 0.078u Elapsed time: 0:01 Version: ImageMagick 6.5.6-5 2009-09-25 Q16 OpenMP http://www.imagemagick.org
Converted:
Image: tj/456c2e75fe0faa57fd1cfd87117e0963/p1.jpg Format: JPEG (Joint Photographic Experts Group JFIF format) Class: DirectClass Geometry: 500x700+0+0 Resolution: 100x100 Print size: 5x7 Units: PixelsPerInch Type: TrueColor Endianess: Undefined Colorspace: RGB Depth: 8-bit Channel depth: red: 8-bit green: 8-bit blue: 8-bit Channel statistics: red: min: 0 (0) max: 255 (1) mean: 216.75 (0.849999) standard deviation: 50.1075 (0.1965) kurtosis: 4.066 skewness: -2.03195 green: min: 0 (0) max: 255 (1) mean: 158.316 (0.620846) standard deviation: 89.1433 (0.349582) kurtosis: -1.17694 skewness: -0.52022 blue: min: 0 (0) max: 255 (1) mean: 113.58 (0.445411) standard deviation: 96.3298 (0.377764) kurtosis: -1.53577 skewness: 0.287937 Image statistics: Overall: min: 0 (0) max: 255 (1) mean: 122.161 (0.479064) standard deviation: 106.052 (0.415889) kurtosis: -1.7498 skewness: 0.00808184 Rendering intent: Undefined Interlace: None Background color: white Border color: rgb(223,223,223) Matte color: grey74 Transparent color: black Page geometry: 500x700+0+0 Dispose: Undefined Iterations: 0 Compression: JPEG Quality: 92 Orientation: Undefined Properties: date:create: 2010-10-22T10:27:18+08:00 date:modify: 2010-10-22T10:31:08+08:00 jpeg:colorspace: 2 jpeg:sampling-factor: 2x2,1x1,1x1 signature: 63202ddf9106d3374fe3a396f5105ce8099051cf807ceb2ab5a19532957cec10 Artifacts: verbose: true Tainted: False Filesize: 174kb Number pixels: 342kb Version: ImageMagick 6.5.6-5 2009-09-25 Q16 OpenMP http://www.imagemagick.org
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