Legacy ImageMagick Discussions Archive

It's actually a client's server and they claim it has been allocated loads of RAM (16GB) and CPU. However, it is virtual so I guess it will be competing with other virtual servers they have running on the same hardware. Any ideas for how I can test/prove the resources available at the time of ...

We are converting single pages of a multi-page TIFF to JPEG using ImageMagick-6.8.0-2-Q16-windows-x64. A typical conversion takes less than a second on our test (physical) servers and indeed on my laptop. On a production server, which is higher spec but virtual, a typical conversion takes around 5 ...

If you just need the name of the colorspace, you could use:
identify -format "%r" myimage.jpg

How about extending the -format options available to identify so it is possible to find out if an alpha channel is 'unspecified', 'unassociated' or 'associated'? Perhaps the current %A option could return one these three values (in place of 'True') or 'False' (if there's no alpha channel, i.e. as it ...

Here's what I have discovered so far. Photoshop stores transparency in an 'associated' alpha channel and selections in 'unassociated' alpha channels, as per the TIFF spec. If a TIFF has both transparency and selections, it looks like Photoshop always stores the associated alpha channel first. From ...

to convert an image with an alpha channel such as png or tiff to white background as jpg, try convert image.tif -background white -flatten image.jpg Yes - you'll see from my initial post that this is the command I use to convert a TIFF containing a transparent background to a JPEG with a white ...

Thanks - that's very helpful.

I'm also exploring using the fact that Photoshop seems to use the XMP field Photoshop:AlphaChannelsNames to store the names of channels used to store selections, and one called 'Transparency' if it uses an alpha channel to store transparency information.

Regards,
Martin

So I should build in a check to get the input profile, and use this input profile to convert the image to sRGB. If the image contains the 'source' profile (i.e. fully embedded in it, not just the name) then you need only specify the 'destination' profile: if you specify only one -profile flag then ...

... and JPEG does NOT support transparency (alpha channels) at all. I realise that - that's why I want to figure out how to convert an alpha channel used for transparency to a white background (when converting to JPEG) but discard an alpha channel used for Photoshop selections. However, I don't ...

I am trying to figure out how to convert various TIFF files to JPEGs using one IM command. The problem is that the TIFFs were created with Photoshop and some contain an alpha channel representing transparency while others contain one of more alpha channels (I think) storing mask/selection ...

Thanks Anthony - this is helpful.

> It looks to me like the alpha channel of the TGA image is NOT an alpha channel, but just a masking channel of some sort.

That's probably right - for example, I think Photoshop uses an alpha channel to 'store' selections.

Do you see any errors in the PHP logs, for example failure to load the Ghostscript dll? I don't know much about PHP but if IM can find GS when you run it from the command line (outside PHP) then it looks like IM knows where GS is - so perhaps the process that's running IM from PHP doesn't have ...

Although removing the alpha channel solves xmovie's problem, shouldn't convert be able to resize an image that contains an alpha channel without changing the other 3 channels (it seems to merge in the alpha channel, in most cases making the 'opaque' parts black)? Is this a bug? I have noticed that ...

This is happening because your image (a.tga) contains an alpha channel - IM seems to merge this into the channels of the resulting image (not sure what it's doing exactly, or why - anyone?) You can tell IM to ignore the alpha channel using -alpha option, for example: convert a.tga -alpha Off -resize ...

Are you seeing any other errors, e.g. from Ghostscript? We have had various issues with GS when converting PDFs - most have been fixed by upgrading GS. I am using version 8.63 - your PDF converts fine for me (on Windows).
Regards,
Martin