First: Can someone tell me what are the latest available binaries? I'm using the Q16 Windows static binaries, on Windows XP - the IM version is probably v6.6.1-5. I think there are small inconstancies with the version numbers on the download page/filenames and the numbers that IM itself reports. On my system, "convert -version" currently says:
Version: ImageMagick 6.6.1-6 2010-04-23 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2010 ImageMagick Studio LLC
Features: OpenMP
But I still believe it's version 6.6.1-5.(?)
The 'software' list in Windows reported that version (downloaded at April 24th) as:
"ImageMagick 6.6.1-5 Q16 (2010-05-01)"
I'm confused..

Now to some of my problems:
Case 1:
A plain 24bit BMP (sample taken from this thread):
http://www.tmace.com/viewer.php?file=51 ... 444716.bmp
"identify -verbose":
Type: Palette
Colorspace: RGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
Channel statistics:
...
(By the way, type "Palette" seems strange to me - as the file is stored as normal 3x8bit, so I would expect "TrueColor". But probably identify shows the values of the in-memory image - not the actual file representation. Is that correct?)
Now if I use the following command to create an alpha channel (set to opaque):
convert test.bmp -alpha on teston.png
Identify shows that:
Type: PaletteMatte
Colorspace: RGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
alpha: 8-bit
Channel statistics:
...
Alpha:
min: 0 (0)
max: 1 (0.00392157)
mean: 4.64511e-005 (1.82161e-007)
...
Histogram:
43054: (224, 9, 29,255) #E0091D rgba(224,9,29,1)
2: (224, 9, 29,254) #E0091DFE rgba(224,9,29,0.996078)
...

A command with "-alpha set" instead of "-alpha on" seems to work:
Type: PaletteMatte
Colorspace: RGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
alpha: 1-bit
Channel statistics:
...
Alpha:
min: 0 (0)
max: 0 (0)
mean: 0 (0)
...
Histogram:
43056: (224, 9, 29,255) #E0091D rgba(224,9,29,1)
...
I'm not sure anymore if some values represent alpha or opacity, but the identify output and the actual file look ok.
I just think (as the input file has no pre-existing alpha channel) that both commands should produce the same output..?
Case 2:
Just an example that shows that "-alpha on" can work. It's basically the same image as above - saved with a different software:
http://www.tmace.com/viewer.php?file=19 ... 045860.bmp
Actually, I would call this file 'TrueColorMatte' - it comes with an alpha channel. But ImageMagick doesn't recognize this channel - belongs probably to this thread. Anyway, IM treats it as an image without alpha - like in Case 1. Identify:
Type: Palette
Colorspace: RGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
Channel statistics:
...
Here, "-alpha on" produces the same output as "-alpha set":
Type: PaletteMatte
Colorspace: RGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
alpha: 1-bit
...
Alpha:
min: 0 (0)
max: 0 (0)
mean: 0 (0)
...
Histogram:
43056: (224, 9, 29,255) #E0091D rgba(224,9,29,1)
...
(The behaviour in case 1 and case 2 doesn't show just for these two files. It can be done with e.g. internal IM images, too.)
Case 3:
Also about the alpha channel.. This time, ImageMagick 'invents' alpha channels out of the blue. (Probably it's not related to the above issues.)
I have this issue whenever I do color conversions (with color profiles). I think it always occurs when there is a color profile present.
One can take a random image from the web - for example:
http://www.pbase.com/kevin_ve/image/60070066/original
As it's a JPG, it has no alpha channel of course. Identify:
Type: TrueColor
Colorspace: RGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
Channel statistics:
...
Profile-icc: 3144 bytes
Description: sRGB IEC61966-2.1
...
Now, after a simple "convert input.jpg output.bmp", identify shows this:
Type: TrueColorMatte
Colorspace: RGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
alpha: 1-bit
...
Alpha:
min: 0 (0)
max: 0 (0)
mean: 0 (0)
...
At this step, my output.bmp doesn't seem to contain any alpha channel. But identify thinks it does.
I can make a second conversion ("convert output.bmp output2.bmp"): Now not only identify shows an alpha channel (the identify output stays the same), but the file really contains one.
Case 4:
The issues can even partly be 'summarized' with a command like that:
"convert rose: -profile sRGB.icm rose.bmp"
Identify says:
Type: TrueColorMatte
Colorspace: RGB
Depth: 8/16-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
alpha: 16-bit
...
Alpha:
min: 0 (0)
max: 1 (0.00303655)
mean: 0.000240472 (9.43027e-007)
...

I hope that most of that rather longish post was understandable (English is not my mother tongue).
I would be glad if some users here could affirm some of the things - or give hints if I made something wrong.
Eventually, I will create (separate) threads for the issues in the bug forum.