Legacy ImageMagick Discussions Archive

Hi,

I have here some bmp graphics with transparency which I want to convert into png. I tried it with "-channel rgba", "-alpha set" and "-matte", but sadly I don't get the right transparency values. Conversion via Gimp works.
Tested with IM 6.6.5-0 and IM 6.6.7-4 on windows.

Link to test graphic "27.bmp":

http://storeplace.org/img/show.php/3305_27.bmp.html

bmp is such a shitty format...


-
indiego

when I download and look at the verbose information, it does not show any transparency. Perhaps your upload host cannot store it with transparency. check your image

identify -verbose 27.bmp

does that show any transparency?

Mh, strange. I just downloaded the graphic via right mouse button menu (save as...). Checked the bmp with gimp and it looked ok. "identify -verbose 27.bmp" gives

• Image: 27.bmp
  Format: BMP (Microsoft Windows bitmap image)
  Class: DirectClass
  Geometry: 348x36+0+0
  Units: PixelsPerCentimeter
  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: 101.879 (0.399527)
  standard deviation: 86.066 (0.337514)
  kurtosis: -1.09022
  skewness: 0.376069
  Green:
  min: 0 (0)
  max: 255 (1)
  mean: 107.189 (0.420348)
  standard deviation: 86.5704 (0.339492)
  kurtosis: -1.1724
  skewness: 0.241687
  Blue:
  min: 0 (0)
  max: 255 (1)
  mean: 110.716 (0.434182)
  standard deviation: 87.2461 (0.342142)
  kurtosis: -1.22485
  skewness: 0.153457
  Image statistics:
  Overall:
  min: 0 (0)
  max: 255 (1)
  mean: 106.595 (0.418019)
  standard deviation: 86.6289 (0.339721)
  kurtosis: -1.16755
  skewness: 0.25694
  Histogram:
  3218: ( 0, 0, 0) #000000 black
  .....
  4: (254,254,255) #FEFEFF rgb(254,254,255)
  935: (255,255,255) #FFFFFF white
  Rendering intent: Undefined
  Interlace: None
  Background color: white
  Border color: rgb(223,223,223)
  Matte color: grey74
  Transparent color: black
  Compose: Over
  Page geometry: 348x36+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: Undefined
  Orientation: Undefined
  Properties:
  date:create: 2011-02-02T19:31:55+01:00
  date:modify: 2011-02-02T19:31:55+01:00
  signature: 1e9223b7fb2697b7ab61fa576c6eca4c9393488f4841b8d283c9048da9c99971
  Artifacts:
  verbose: true
  Tainted: False
  Filesize: 50.2KBB
  Number pixels: 12.5KB
  Pixels per second: 12.51MB
  User time: 0.000u
  Elapsed time: 0:01.001
  Version: ImageMagick 6.6.7-4 2011-01-29 Q16 http://www.imagemagick.org

In the above verbose info, IM shows no alpha channel or alpha colors and the type is truecolor and not truecolormatte. So something is odd about the bmp file or IM interpretation of it. What version BMP is it? BMP2, BMP3 or BMP4. See http://www.imagemagick.org/Usage/formats/#bmp

Sorry, I have no special BMP tool to extract more info. As this graphic is part of the Windows7 Explorer I expect the latest and greatest from MS (probably BMP5). Anyhow, the graphic seems to be valid and it looks like this format is currently not supported in IM. As nobody (except MS) is using this shitty format I can not expect that IM will support it. Gimp works, so I will have to do a manual conversion, one by one.

fmw42, thanks for taking the time to look into it!

-
indiego

You should report this to the bugs or developers forum and see what they say.