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#1 2012-07-25 04:20:40

PhirripSyrrip
Scratcher
Registered: 2012-02-11
Posts: 100+

Compressing Images.

What does it mean when I get the option to "compress sounds and images" when I share a project? What are the good and bad things about that?


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#2 2012-07-25 04:24:52

SciTecCf
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Registered: 2011-11-23
Posts: 1000+

Re: Compressing Images.

The good thing is that the project is usually smaller.

The bad thing is, if they're already compressed, they are decompressed and compressed again, lowering the quality further. I would recommend compressing it manually, Edit --> Compress (Sounds/Images)..., and then unchecking it.


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#3 2012-07-30 22:07:15

SJRCS_011
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Registered: 2011-02-07
Posts: 1000+

Re: Compressing Images.

SciTecCf wrote:

The good thing is that the project is usually smaller.

The bad thing is, if they're already compressed, they are decompressed and compressed again, lowering the quality further. I would recommend compressing it manually, Edit --> Compress (Sounds/Images)..., and then unchecking it.

Actually, Scratch will prevent something from being comprssed twice.  Anyway, I think what PhirripSyrup was wondering was what exactly is compression.

Compression is when a program makes a file size smaller through two methods.  One, lossless compression, combines similar bytes into one byte, lowering the filesize.
Here are the pros and cons of lossless compression:
Pros: No detail lost after decompressing
Cons: doesn't lower filesize as much

The other type is lossy compression.  Lossy compression eliminates detail in files instead of combining similar bytes.  Here are the pros and cons of lossy compression:
Pros: Filesize is much smaller
Cons: a lot of detail can be lost.

Now, I believe Scratch uses a mix of lossy and lossless compression.  So, if you project is under 10MB uncompressed, unchecking the box would improve it's quality while still being able to upload.

On the other hand, if you are nearing the 10MB mark, then you may want to check it to make sure you get under the limit.

and sorry for the bump if this was already resolved.  smile

Last edited by SJRCS_011 (2012-07-30 22:08:19)


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#4 2012-07-31 14:54:13

BoltBait
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Registered: 2009-03-09
Posts: 1000+

Re: Compressing Images.

If your project uses any of the:

<touching color [#00FF00]?>
You should never compress images.  Compressing images sometimes changes the colors of your images slightly and will cause the "touching color" blocks to fail.

Last edited by BoltBait (2012-07-31 14:55:03)


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#5 2012-07-31 15:07:14

stevetheipad
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Registered: 2011-08-06
Posts: 1000+

Re: Compressing Images.

BoltBait wrote:

If your project uses any of the:

<touching color [#00FF00]?>
You should never compress images.  Compressing images sometimes changes the colors of your images slightly and will cause the "touching color" blocks to fail.

Good point, I will keep this in mind myself.  smile


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#6 2012-07-31 20:20:47

PhirripSyrrip
Scratcher
Registered: 2012-02-11
Posts: 100+

Re: Compressing Images.

Thanks SJRCS_011, BoltBait and SciTecCf, you're posts we're helpful and interesting.


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#7 2012-08-01 09:20:31

chrisbown
Scratcher
Registered: 2011-07-29
Posts: 100+

Re: Compressing Images.

stevetheipad wrote:

BoltBait wrote:

If your project uses any of the:

<touching color [#00FF00]?>
You should never compress images.  Compressing images sometimes changes the colors of your images slightly and will cause the "touching color" blocks to fail.

Good point, I will keep this in mind myself.  smile

i have seen that, the colour quality goes down and sometimes slightly change.


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