Author Topic: .bmp to .jpg conversion  (Read 8165 times)

Offline choronr

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.bmp to .jpg conversion
« on: June 09, 2011, 10:57:54 PM »
I have a 'Photoshop' question. I have an 1830 x 1024 .bmp file that I want to save as a .jpg file. My limit in size for posting is 512KB. In Photoshop, settings for max quality is 12 - this yields a .jpg size of over 600KB (too large).

When I bring the quality down to 11, it yields a .jpg size of little more than 300 (too small). Unless I'm missing something, I cannot find a way to get something closer to 512KB other than resizing the image. Any suggestions on this?

It seems there is no way to adjust the settings so as to save a .bmp to a .jpg that is incrementally somewhere between 11 and 12 as such to achieve a file KB somewhere close to 512KB without resizing the image. I have Photoshop 7.0.

          Bob  

Offline Oshyan

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Re: .bmp to .jpg conversion
« Reply #1 on: June 09, 2011, 11:08:29 PM »
The "12" setting is actually rather wasteful and doesn't really get you any more *noticeable* quality. It's *not* intended for posting to the web, like the forums here. In fact for web posting you should not use the regular Save As at all, instead you should use Save for Web (I believe Photoshop 7 should have this feature). This will give you the best balance of size and quality *and* give you the ability to see exactly what effect your compression settings will have, so you can be sure the quality is acceptable.

It's also important to note that just because there's a maximum doesn't mean you need to *hit* the maximum (or get close to it). It sounds like you're trying to be as close to 512KB as possible, but why? If the quality is good at 100KB for your image, why use extra space unnecessarily? It just makes downloads take longer for viewers and takes up more space for whomever is hosting the image. Particularly with lower resolution images the file size doesn't need to be as large.

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Offline choronr

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Re: .bmp to .jpg conversion
« Reply #2 on: June 09, 2011, 11:16:32 PM »
Thanks Oshyan. I checked Photoshop and I don't see a 'Save for Web' option. When I tried the lower quality number (11), the sky in the image showed banding. At the 12 setting, the banding was gone. Under 'Haze glow Power' I had reduced it from the default of 1.25 to 0.75.

Sorry, I did find 'Save for Web' ...my error. I will try it.
« Last Edit: June 09, 2011, 11:18:30 PM by choronr »

Offline choronr

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Re: .bmp to .jpg conversion
« Reply #3 on: June 09, 2011, 11:30:19 PM »
Ok, I opened the .bmp in Photoshop and Saved for Web. Apparently it converts it to a .gif. But, the bottom portion of the image is cut off ...what's this?

Offline Henry Blewer

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Re: .bmp to .jpg conversion
« Reply #4 on: June 10, 2011, 01:30:15 AM »
Do you have Corel Paint X2? That has a very good wizard exporter. Or try GIMP (Free). It also does a very good job.
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Offline choronr

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Re: .bmp to .jpg conversion
« Reply #5 on: June 10, 2011, 01:34:46 AM »
Do you have Corel Paint X2? That has a very good wizard exporter. Or try GIMP (Free). It also does a very good job.

Thanks Henry, I don't have either program; I only have 'Paint' and 'Photoshop'. I did a final save as a .jpg after screwing around with different PS adjustments. Still have some banding in the sky however; but, what you see is what you get.

Offline rageracer

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Re: .bmp to .jpg conversion
« Reply #6 on: June 10, 2011, 01:49:23 AM »
Not sure if this will help, but if your just resizing or converting to jpg, why don't you try irfanview

Code: [Select]
http://www.irfanview.com/

Offline choronr

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Re: .bmp to .jpg conversion
« Reply #7 on: June 10, 2011, 01:51:30 AM »
Not sure if this will help, but if your just resizing or converting to jpg, why don't you try irfanview

Code: [Select]
http://www.irfanview.com/
Thanks, I forgot I had Irfanview; I'll give it a try.

Offline freelancah

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Re: .bmp to .jpg conversion
« Reply #8 on: June 10, 2011, 10:06:22 AM »
Photoshop save as, jpg and quality 10 is usually something that yields good enough results and does not consume too much space..Well atleast thats what I've been using with results to my liking

Offline Dune

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Re: .bmp to .jpg conversion
« Reply #9 on: June 10, 2011, 12:52:24 PM »
I always use Irfanview (save for web plugin) for these posts, as you can exactly see the number of kB's corresponding to the quality.
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Offline choronr

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Re: .bmp to .jpg conversion
« Reply #10 on: June 10, 2011, 05:12:37 PM »
Photoshop save as, jpg and quality 10 is usually something that yields good enough results and does not consume too much space..Well atleast thats what I've been using with results to my liking
Thanks for your thoughts on this, I've always used this method; but, will have a look at the Irfanview method and see if it produces better results.

Offline choronr

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Re: .bmp to .jpg conversion
« Reply #11 on: June 10, 2011, 05:16:15 PM »
Photoshop save as, jpg and quality 10 is usually something that yields good enough results and does not consume too much space..Well atleast thats what I've been using with results to my liking
Thanks for your thoughts on this, I've always used this method; but, will have a look at the Irfanview method and see if it produces better results.
Thanks Ulco, I need to upload the Irfanview RIOT.dll PLUGIN to try this method. The same method from Photoshop produced horrible results with very bad banding in the sky. 

Offline Oshyan

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Re: .bmp to .jpg conversion
« Reply #12 on: June 10, 2011, 10:12:47 PM »
Save for Web allows you to choose JPG as one of the output formats, so I'd suggest trying that again and looking for a "format" option or "file type", etc. Irfanview is one option, XnView is another (my preference). In XnView you can get great results without too large file by doing the following:

File->Export
Go to JPG tab (if not already there)
Quality to 90 or 95 if necessary
Change DCT method to "Float (best but slowest)"
Smoothing factor 0
Subsampling factor to "1x1, 1x1, 1x1 (best quality)"
Progressive enabled (you don't have to use progressive, it won't really affect quality, but can make slightly smaller file size on large images)
Optimize Huffman table enabled

Click the magnifying glass in the middle of the two preview images above to get to 100% view, then click and drag around on either of the image previews to pan around the image and see if there are any compression artifacts. The compressed version is on the right, the original on the left.

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Offline choronr

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Re: .bmp to .jpg conversion
« Reply #13 on: June 10, 2011, 10:23:19 PM »
Save for Web allows you to choose JPG as one of the output formats, so I'd suggest trying that again and looking for a "format" option or "file type", etc. Irfanview is one option, XnView is another (my preference). In XnView you can get great results without too large file by doing the following:

File->Export
Go to JPG tab (if not already there)
Quality to 90 or 95 if necessary
Change DCT method to "Float (best but slowest)"
Smoothing factor 0
Subsampling factor to "1x1, 1x1, 1x1 (best quality)"
Progressive enabled (you don't have to use progressive, it won't really affect quality, but can make slightly smaller file size on large images)
Optimize Huffman table enabled

Click the magnifying glass in the middle of the two preview images above to get to 100% view, then click and drag around on either of the image previews to pan around the image and see if there are any compression artifacts. The compressed version is on the right, the original on the left.

- Oshyan
Thank you Oshyan, and for the details. I will have a look at XnView and decide where I'll be going with this. I've never been really happy with the .bmp > Photoshop > .jpg; then, putts around trying to get the best results. PS does not give you the KB size of the .jpg converted from the .bmp. I would have to take the .jpg image into 'Paint' in order to find out the KB size.

Offline Oshyan

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Re: .bmp to .jpg conversion
« Reply #14 on: June 10, 2011, 10:55:37 PM »
XnView gives a nice realtime update of the visual quality and resulting file size. It also gives you more options to play with than even modern Photoshop (CS5) with Save for Web. I loves my XnView. ;D

- Oshyan