why image's depth changed?

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cndep
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Joined: 2011-03-06T06:20:13-07:00
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why image's depth changed?

Post by cndep » 2011-03-08T04:03:25-07:00

I use this version:ImageMagick-6.6.0


convert -resize 50% bild.bmp test.bmp

the depth of the origin image is 4 bits,after convert the resulting image's depth is changed to 24,why?

I tried this:

convert -resize 50% -depth 4 bild.bmp test.bmp

but it does'nt work.

And I did some code:

while (MagickNextImage(magick_wand) != MagickFalse)
{
MagickScaleImage(magick_wand, iWidth, iHeight);
//after this the depth of the origin image is changed from 4 to 24 bits
}

I tried MagickSetImageDepth(magick_wand,4),but it does'nt work,why?

Code: Select all

while (MagickNextImage(magick_wand) != MagickFalse)
{
	MagickScaleImage(magick_wand, iWidth, iHeight);
	MagickSetImageDepth(magick_wand,4);
	blob = MagickGetImageBlob(magick_wand, &length);
	............
}


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fmw42
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Re: why image's depth changed?

Post by fmw42 » 2011-03-08T10:06:16-07:00

try putting the input image first and use BMP3: format

convert bild.bmp -resize 50% -depth 4 BMP3:test.bmp

see http://www.imagemagick.org/Usage/formats/#bmp for depth restrictions

cndep
Posts: 3
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Re: why image's depth changed?

Post by cndep » 2011-03-08T17:40:44-07:00

fmw42 wrote:try putting the input image first and use BMP3: format

convert bild.bmp -resize 50% -depth 4 BMP3:test.bmp

see http://www.imagemagick.org/Usage/formats/#bmp for depth restrictions

Thanks,I tried,but it does'nt work.

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fmw42
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Re: why image's depth changed?

Post by fmw42 » 2011-03-08T17:49:34-07:00

Post a link to your image so others can test. You might try upgrading your IM to the latest version.

Also try

convert bild.bmp -resize 50% +dither -colors 16 -depth 4 BMP3:test.bmp

Note resize will interpolate colors to more than you started. So you need to force it back to 16 colors and depth 4.

You could try

convert bild.bmp -sample 50% BMP3:test.bmp

-sample will not interpolate colors, but will choose the closest color.



But this works for me on IM 6.6.8.1 Q16 Mac OSX Tiger

# create 4-bit png
convert rose: -colors 16 +dither -depth 4 rose.png
identify -verbose rose.png
Image: rose.png
Format: PNG (Portable Network Graphics)
Class: PseudoClass
Geometry: 70x46+0+0
Resolution: 72x72
Print size: 0.972222x0.638889
Units: Undefined
Type: Palette
Endianess: Undefined
Colorspace: RGB
Depth: 8/4-bit
Channel depth:
red: 4-bit
green: 4-bit
blue: 4-bit

Channel statistics:
Red:
min: 51 (0.2)
max: 238 (0.933333)
mean: 143.83 (0.564037)
standard deviation: 68.6489 (0.269211)
kurtosis: -1.41232
skewness: 0.0822659
Green:
min: 51 (0.2)
max: 238 (0.933333)
mean: 88.4739 (0.346957)
standard deviation: 52.5254 (0.205982)
kurtosis: 1.59146
skewness: 1.55269
Blue:
min: 34 (0.133333)
max: 238 (0.933333)
mean: 80.7658 (0.316729)
standard deviation: 52.2382 (0.204856)
kurtosis: 2.95706
skewness: 2.00768
Image statistics:
Overall:
min: 34 (0.133333)
max: 238 (0.933333)
mean: 104.356 (0.409241)
standard deviation: 58.3107 (0.22867)
kurtosis: 0.967865
skewness: 1.37136
Histogram:
54: ( 51, 51, 34) #333322 rgb(51,51,34)
363: ( 51, 51, 51) #333333 grey20
235: ( 51, 68, 51) #334433 rgb(51,68,51)
98: ( 85, 68, 51) #554433 rgb(85,68,51)
84: ( 85,136, 68) #558844 rgb(85,136,68)
241: (102, 51, 51) #663333 rgb(102,51,51)
270: (102,102, 85) #666655 rgb(102,102,85)
184: (119,153, 85) #779955 rgb(119,153,85)
153: (136,136,153) #888899 rgb(136,136,153)
247: (153, 51, 51) #993333 rgb(153,51,51)
116: (170,170,187) #AAAABB rgb(170,170,187)
118: (187, 68, 68) #BB4444 rgb(187,68,68)
340: (204, 51, 51) #CC3333 rgb(204,51,51)
249: (238, 51, 51) #EE3333 rgb(238,51,51)
268: (238, 85, 85) #EE5555 rgb(238,85,85)
200: (238,238,238) #EEEEEE rgb(238,238,238)
Colormap: 16
...



#convert 4-bit png to 4-bit bmp
convert rose.png +dither -colors 16 -depth 4 BMP3:rose.bmp
identify -verbose rose.bmp
Image: rose.bmp
Format: BMP (Microsoft Windows bitmap image)
Class: PseudoClass
Geometry: 70x46+0+0
Resolution: 28.34x28.34
Print size: 2.47001x1.62315
Units: PixelsPerCentimeter
Type: Palette
Endianess: Undefined
Colorspace: RGB
Depth: 4-bit
Channel depth:
red: 4-bit
green: 4-bit
blue: 4-bit

Channel statistics:
Red:
min: 3 (0.2)
max: 14 (0.933333)
mean: 8.46056 (0.564037)
standard deviation: 4.03817 (0.269211)
kurtosis: -1.41232
skewness: 0.0822659
Green:
min: 3 (0.2)
max: 14 (0.933333)
mean: 5.20435 (0.346957)
standard deviation: 3.08973 (0.205982)
kurtosis: 1.59146
skewness: 1.55269
Blue:
min: 2 (0.133333)
max: 14 (0.933333)
mean: 4.75093 (0.316729)
standard deviation: 3.07283 (0.204856)
kurtosis: 2.95706
skewness: 2.00768
Image statistics:
Overall:
min: 2 (0.133333)
max: 14 (0.933333)
mean: 6.13861 (0.409241)
standard deviation: 3.43004 (0.22867)
kurtosis: 0.967865
skewness: 1.37136
Histogram:
54: ( 51, 51, 34) #333322 rgb(51,51,34)
363: ( 51, 51, 51) #333333 grey20
235: ( 51, 68, 51) #334433 rgb(51,68,51)
98: ( 85, 68, 51) #554433 rgb(85,68,51)
84: ( 85,136, 68) #558844 rgb(85,136,68)
241: (102, 51, 51) #663333 rgb(102,51,51)
270: (102,102, 85) #666655 rgb(102,102,85)
184: (119,153, 85) #779955 rgb(119,153,85)
153: (136,136,153) #888899 rgb(136,136,153)
247: (153, 51, 51) #993333 rgb(153,51,51)
116: (170,170,187) #AAAABB rgb(170,170,187)
118: (187, 68, 68) #BB4444 rgb(187,68,68)
340: (204, 51, 51) #CC3333 rgb(204,51,51)
249: (238, 51, 51) #EE3333 rgb(238,51,51)
268: (238, 85, 85) #EE5555 rgb(238,85,85)
200: (238,238,238) #EEEEEE rgb(238,238,238)
Colormap: 16
...

This also works:


convert logo: -resize 50% +dither -colors 16 -depth 4 BMP3:logo.bmp
identify -verbose logo.bmp

Image: logo.bmp
Format: BMP (Microsoft Windows bitmap image)
Class: PseudoClass
Geometry: 320x240+0+0
Resolution: 28.34x28.34
Print size: 11.2915x8.4686
Units: PixelsPerCentimeter
Type: Palette
Endianess: Undefined
Colorspace: RGB
Depth: 4-bit
Channel depth:
red: 4-bit
green: 4-bit
blue: 4-bit

Channel statistics:
Red:
min: 1 (0.0666667)
max: 15 (1)
mean: 13.4754 (0.898359)
standard deviation: 3.94559 (0.26304)
kurtosis: 4.20909
skewness: -2.43552
Green:
min: 1 (0.0666667)
max: 15 (1)
mean: 13.3053 (0.887021)
standard deviation: 4.00473 (0.266982)
kurtosis: 3.06801
skewness: -2.16451
Blue:
min: 1 (0.0666667)
max: 15 (1)
mean: 13.5012 (0.900082)
standard deviation: 3.60552 (0.240368)
kurtosis: 4.3518
skewness: -2.35881
Image statistics:
Overall:
min: 1 (0.0666667)
max: 15 (1)
mean: 13.4273 (0.895154)
standard deviation: 3.85596 (0.257064)
kurtosis: 3.8738
skewness: -2.32518
Histogram:
1762: ( 17, 17, 17) #111111 rgb(17,17,17)
1585: ( 34, 34,102) #222266 rgb(34,34,102)
325: ( 34, 51,136) #223388 rgb(34,51,136)
2735: ( 34, 68,153) #224499 rgb(34,68,153)
143: ( 51, 85,136) #335588 rgb(51,85,136)
749: ( 85, 68, 34) #554422 rgb(85,68,34)
804: ( 85,102,102) #556666 rgb(85,102,102)
252: (119,136,119) #778877 rgb(119,136,119)
1064: (153,153,170) #9999AA rgb(153,153,170)
568: (204,102, 68) #CC6644 rgb(204,102,68)
1040: (221,170, 85) #DDAA55 rgb(221,170,85)
779: (221,204,204) #DDCCCC rgb(221,204,204)
295: (238,170,170) #EEAAAA rgb(238,170,170)
755: (238,238,238) #EEEEEE rgb(238,238,238)
783: (255, 17, 17) #FF1111 rgb(255,17,17)
63161: (255,255,255) #FFFFFF white
Colormap: 16
...

cndep
Posts: 3
Joined: 2011-03-06T06:20:13-07:00
Authentication code: 8675308

Re: why image's depth changed?

Post by cndep » 2011-03-09T20:33:25-07:00

Thanks very much,the two methods both works.

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