Legacy ImageMagick Discussions Archive

Hello everyone,

I've just installed the 6.6 version of imagemagick and noticed that when i execute the verbose command it doesn't detect anymore the alpha channel even using the -format %A parameter it returns a false statement. see below verbose output of a test image with alpha channel.

Image: test_alpha.tif
Format: TIFF (Tagged Image File Format)
Class: DirectClass
Geometry: 1102x864+0+0
Resolution: 188.88x188.88
Print size: 5.83439x4.57433
Units: PixelsPerInch
Type: TrueColor
Base type: TrueColor
Endianess: MSB
Colorspace: RGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
Channel statistics:
Red:
min: 0 (0)
max: 65279 (1)
mean: 153.784 (0.603073)
standard deviation: 50.7549 (0.199039)
kurtosis: 0.153505
skewness: -0.288556
Green:
min: 0 (0)
max: 65279 (1)
mean: 149.425 (0.585982)
standard deviation: 56.0807 (0.219924)
kurtosis: -0.662065
skewness: -0.108865
Blue:
min: 0 (0)
max: 65279 (1)
mean: 104.951 (0.411574)
standard deviation: 76.5669 (0.300262)
kurtosis: -0.900334
skewness: 0.838951
Image statistics:
Overall:
min: 0 (0)
max: 65279 (1)
mean: 102.04 (0.400157)
standard deviation: 82.0473 (0.321754)
kurtosis: -1.26869
skewness: 0.181201
Rendering intent: Undefined

The problem may be specific to your image (we're getting alpha channel statistics for our images). Post a URL to your image so we can download and inspect it.

here it is..
http://www.clipartof.com/images/free_ho ... alpha.tiff

im using Imagemagick 6.6.0 Q16 on Windows XP SP2

Hello magick any news on this?

The problem is fixed. We'll get a new point release out within the next few days.

additional concern on the same test image above regarding removing the alpha channel some pixels from the rgb channel were also removed i'm not sure though if i have the correct syntax

syntax:
convert test_alpha.tiff -background white -flatten +matte test_alpha_removed.tiff

here's the output:
http://www.clipartof.com/images/free_ho ... moved.tiff

and the screenshot comparison:
http://www.clipartof.com/images/free_ho ... enshot.jpg

ImageMagick is behaving properly. The -flatten option blends the background color with the image with the Over composite operator. Perhaps Photoshop is using a different blend operator.

version 6.6.0-3 resolves alpha detection issue thanks magick appreciate the help!

as for the removal of alpha channel i figure i should have only used +matte instead of adding -flatten to avoid blending problems.

Would it be possible to detect alpha channel on grayscale images?