Legacy ImageMagick Discussions Archive

Hi
I'm new to ImageMagick, and have a few questions about quantum levels (Q8 + Q16).
I'll be using PerlMagick and Windows 7 Home Premium.

Q1. Should I install Q8 or Q16?
(I know that Q16 is recommended on the download page)

Q2. What are the pros and cons of Q8 and Q16?
(Apart from the 8-/16-bits-per-pixel per channel)

Q3. Can Q16 manipulate 8 bits-per-pixel images?

Q4. When using Q16 to manipulate 8 bits-per-pixel images, will it be faster or slower than using Q8?

Q5. When using Q16 to manipulate 8 bits-per-pixel images, will it be using more precision in the intermediate processing steps and produce more accurate results than using Q8?

Q6. Can I install both Q8 and Q16?

Q7. When using PerlMagick, will it be easy to tell it whether to use Q8 or Q16?

Thanks very much for any help

(I could not find an FAQ, and I tried searching the forums but did not find anything helpful.)

Q1. Should I install Q8 or Q16?
(I know that Q16 is recommended on the download page)

It depends on what you are doing.

Q2. What are the pros and cons of Q8 and Q16?
(Apart from the 8-/16-bits-per-pixel per channel)

Well, that's the only difference. This makes Q8 slightly faster, and it consumes less memory. Q8 can write only Q8 results. Q16 can write Q8 or Q16 results. If you do photographic processing, and use intermediate files between stages, or do a number of IM processes on your images, I suggest Q16.

Q3. Can Q16 manipulate 8 bits-per-pixel images?

Yes.

Q4. When using Q16 to manipulate 8 bits-per-pixel images, will it be faster or slower than using Q8?

Q16 is slightly slower (on my tests).

Q5. When using Q16 to manipulate 8 bits-per-pixel images, will it be using more precision in the intermediate processing steps and produce more accurate results than using Q8?

Yes. Intermediate results, whether written to disk or in memory between IM commands like "-blur" and "-unsharp" and "-gamma", are in the Q-number. Q16 has more precision than Q8.

Q6. Can I install both Q8 and Q16?

Yes. I'm on Windows 8.1. I have seven varieties of v6 available (Q8, Q16, Q32 and Q62, with and without HDRI), and one of v7. I don't put any on my path, but they are in different directories.

Q7. When using PerlMagick, will it be easy to tell it whether to use Q8 or Q16?

I don't know. If you can specify the path to your commands, then yes, it is easy.

Hi snibgo. Thanks very much for your helpful reply.

snibgo wrote:

Q6. Can I install both Q8 and Q16?

Yes. I'm on Windows 8.1. I have seven varieties of v6 available (Q8, Q16, Q32 and Q62, with and without HDRI), and one of v7. I don't put any on my path, but they are in different directories.

Why are you using mainly v6 instead of v7?

Because I haven't yet tested all my scripts and web pages under v7. Until I have done that, v6 is the devil I know and v7 is the devil I don't know.

(But I have converted all my C software to work under either v6 or v7.)

Thanks