Photo resizing test

[ray_parkhurst]

There is some controversy over what the forum software does with different size photos. I'll post 3 photos below:

1296x864
1200x800
900x600

These are all the same photo, just crops from the first.

142631
142632
142633

Edited to add:

In each case, the forum software reduces the image size by 1 pixel in each dimension.

MODS: This is a serious problem for folks who want to see sharp images. I've often wondered why the images on LCF are always a bit blurry, but now I know why. It would be good to find out why this is happening, and fix it.

Here are the same 3 photos hosted by PB...let's see how they look in comparison:

https://i943.photobucket.com/albums/ad273/rparkhurst/1994-P_IIBIE_B.jpg
https://i943.photobucket.com/albums/ad273/rparkhurst/1994-P_IIBIE_BB.jpg
https://i943.photobucket.com/albums/ad273/rparkhurst/1994-P_IIBIE_BC.jpg

OK, these are all shown at correct size, and show full sharpness.

[VAB2013]

Thank you very much Ray for working on this. You wouldn't think 1 pixel would make so much difference, but it does!

[ray_parkhurst]

Thank you very much Ray for working on this. You wouldn't think 1 pixel would make so much difference, but it does!

Yes, it makes a huge difference. The software must interpolate all the data and create new data for each pixel. If the downsizing is done in an integer fashion, ie by 2x or 3x, then the interpolation does not result in reduced sharpness. But anything else causes problems, and the absolute worst downsizing for sharpness is what the forum software is doing, just a tiny downsizing.

[VAB2013]

Ray, just thinking... if the forum is unable to make a change to fix this, is there anything that we can do to resize our photos differently to correct this?

[ray_parkhurst]

Not really. The act of resizing the photos the way the forum is doing it is a "lossy" process and causes irreversible damage to the image. If it can't be fixed, I think the only solution is external hosting by PB or other hosting service.

[jfines69]

Not sure why you are losing any pixels but to me I see no difference in the images... I have never lost any image size when uploading... The only pixels I can think of as being removed would be from the edges and not the core section of the image??? I compared the images between LCF (uploaded images), your inset images and then I did a right click - open image in new tab and it brought up the image on Photo Bucket... I did notice that on your 1st image when I compared the R the uploaded image shows just a touch of the field in the Rs loop but on your inset and Photo Bucket images that section of field does not show??? It may just be my computer??? You used jpgs as your uploaded images... On my 1st click to open the image in the current tab it shows as jpg however on my 2nd click that opens the image in a new tab it shows as php... Have you tried png format???

[ray_parkhurst]

The forum software is not just cropping the image, it's resizing it slightly. Try downloading one of the images I posted from Photobucket, and the same image from the forum, and do the comparison. The forum image is slightly smaller (1 pixel each edge) and visibly less sharp.

[jfines69]

I downloaded them and will give them a better comparison... What is your setting for PPI??? an image at 1575 x 1050 pixel dimensions and 72 PPI will be 21.88 inches x 14.58 inches but at 1575 x 1050 and 600 PPI it is 2.63 x 1.75 inches... Could that be where the issue is???

[ray_parkhurst]

I downloaded them and will give them a better comparison... What is your setting for PPI??? an image at 1575 x 1050 pixel dimensions and 72 PPI will be 21.88 inches x 14.58 inches but at 1575 x 1050 and 600 PPI it is 2.63 x 1.75 inches... Could that be where the issue is???

No, I don't think so. There is no PPI setting for monitors, only for printers. I'm not printing them, just viewing them on the screen.

[VAB2013]

Well Jim - what do you think... should we ask Roger and Peter about this since we can't figure out another way to fix it?

[jfines69]

No, I don't think so. There is no PPI setting for monitors, only for printers. I'm not printing them, just viewing them on the screen.
There is no PPI settings for the monitors because it is all done automatically in the back ground... That is why items larger than the resolution settings for the monitor are able to be displayed... If we view an item at full size then it would be beyond the boundaries and we would have to scroll up/down and left/right!!!

[jfines69]

Well Jim - what do you think... should we ask Roger and Peter about this since we can't figure out another way to fix it?
I'm not sure if Roger will be able to help but Peter should be... I have not been losing any image size so I am not 100% sure it is thru the forums servers??? If it is thru the forum I am not sure it can be changed???

[VAB2013]

Well... all of this is too complicated for me Jim! Would you please start a thread in the Mod Squad for Peter and Roger to see with a link to this thread so we can get their thoughts on what is going on?

[ray_parkhurst]

I'm not sure if Roger will be able to help but Peter should be... I have not been losing any image size so I am not 100% sure it is thru the forums servers??? If it is thru the forum I am not sure it can be changed???

Jim...I'm not sure what you mean by not losing any image size? It seems you don't believe me, so I suggest you try doing the same thing I did...pick a nice sharp photo, smaller than the screen you're viewing with so it doesn't need to be scaled to fit...upload it to the forum...view the pic to see that it is not as sharp as the one you uploaded...then download it to see that the forum has made the pic slightly smaller than your original. Once you do that, perhaps you will believe me and have some motivation to fix the problem?

[VAB2013]

Thank you Ray for working with us to figure out if we can do something about how the forum is resizing photos. I have created a thread in the Mod Squad with a link to your thread here so that Roger and Peter can take a look at it. It looks like Jim may have missed seeing the most recent posts on this thread.

[silver1985]

Could the answer be in the different amount of compression for the jpg images?

[VAB2013]

Could the answer be in the different amount of compression for the jpg images?

Geez silver... I have no idea. I think you are using one of Ray's photos to show us this info - and in this case it is probably okay with Ray to use his images but anything else in the future, please check with Ray first. I sent a PM to Roger and Peter so we can get their help, we should hear back from them soon.

[ray_parkhurst]

Generally, copyright law allows use of photos for educational purposes without permission of the copyright owner. Only requirement is that the owner is credited.

Silver, I have not seen a lot of unsharpness from compression, though indeed it could be an issue.

[jfines69]

Jim...I'm not sure what you mean by not losing any image size? It seems you don't believe me, so I suggest you try doing the same thing I did...pick a nice sharp photo, smaller than the screen you're viewing with so it doesn't need to be scaled to fit...upload it to the forum...view the pic to see that it is not as sharp as the one you uploaded...then download it to see that the forum has made the pic slightly smaller than your original. Once you do that, perhaps you will believe me and have some motivation to fix the problem?
I didn't say I do not believe you... I am trying to figure out where the problem is... Does it have to do with the number of times an image is being compressed or is it something else... Every time an image is sent over the internet it gets compressed and in doing so data gets lost... I can not fix any problem as I am not an administrator... That is why I said Peter should be able to help... I am not sure it is thru the forums servers tho???

[jfines69]

Could the answer be in the different amount of compression for the jpg images?
That is my thought but I am not sure... That is where Peter would have to do some work!!!

[ray_parkhurst]

Every time an image is sent over the internet it gets compressed and in doing so data gets lost

This is simply not true. Digital data transmission is a lossless process.

[jfines69]

This is simply not true. Digital data transmission is a lossless process.
The transmission process is lossless but the compression process prior to transmission is not... Unless specifically designated to not compress data for transmission the compression process is automatic!!!

[ray_parkhurst]

The transmission process is lossless but the compression process prior to transmission is not... Unless specifically designated to not compress data for transmission the compression process is automatic!!!

Are you talking about the compression done by photo editing software? If so, then indeed there can be compression in order to make the file size small enough to fit forum rules. However, you should note that compression does not degrade image quality very much until it is extreme. It's often hard to tell the difference between a 10MB 16-bit TIFF and the same image compressed to a 300kB jpg. I'm not worried about compression. Only thing that bothers me is the fractional resizing of the image. Taking a 1200x800 image and resizing it to 1199x799 doesn't seem like a big deal, but it's pretty much the worst thing you can do!

[jfines69]

No not when editing to size the file down... The compression occurs on all files just before they are transmitted over the internet... It is all done in the back ground and most folks are totally unaware of it unless something happens... The only program I can think of off hand these days that lets you know it is compressing a file is AOL mail... When an image is attached it compresses the file... I look at your photos again in a side by side comparison and still did not see any difference... Is there a particular spot you can point me to??? I also did a side by side of a couple of my pics and did not notice any difference but then my pics are not the same quality as your photos!!!

[ray_parkhurst]

No not when editing to size the file down... The compression occurs on all files just before they are transmitted over the internet... It is all done in the back ground and most folks are totally unaware of it unless something happens... The only program I can think of off hand these days that lets you know it is compressing a file is AOL mail... When an image is attached it compresses the file... I look at your photos again in a side by side comparison and still did not see any difference... Is there a particular spot you can point me to??? I also did a side by side of a couple of my pics and did not notice any difference but then my pics are not the same quality as your photos!!!

Jim...I'm really not sure what you're talking about. Can we run a test to see if this compression is actually happening? Here's my proposal:

PM me with your email
I'll send you an image file by email (I use Earthlink for my email)
You send me the same file back by email (who do you use for email?)

By your description above, the file will be compressed by my mail system, and then it will be compressed by your email system, so the file will be significantly smaller when it comes back to me.

I just did a similar test using Photobucket. I uploaded a photo to PB, and then downloaded the same file, and compared the images. They were exactly the same size, no compression occurred. So it will be interesting to see if the email systems do any compression.

Regarding seeing a difference between the files, please confirm that you see they have been changed in size by 1 pixel on each edge. Can we at least agree on this?

[jfines69]

Jim...I'm really not sure what you're talking about. Can we run a test to see if this compression is actually happening? Here's my proposal:

PM me with your email
I'll send you an image file by email (I use Earthlink for my email)
You send me the same file back by email (who do you use for email?)

By your description above, the file will be compressed by my mail system, and then it will be compressed by your email system, so the file will be significantly smaller when it comes back to me.

I just did a similar test using Photobucket. I uploaded a photo to PB, and then downloaded the same file, and compared the images. They were exactly the same size, no compression occurred. So it will be interesting to see if the email systems do any compression.

Regarding seeing a difference between the files, please confirm that you see they have been changed in size by 1 pixel on each edge. Can we at least agree on this?
I see the loss of a pixel which is strange... The only thing I haven't been able to find is a less detailed area on the photos when I do a side by side comparison... Is it the entire photo or just certain parts you are loosing detail??? When you embed the photo in your post are you embedding the actual photo From Computer or is it a link to photo bucket From URL??? When I click on the embedded photo I get a new tab and it takes me directly to photo bucket even when I right click and click Open Image in New Tab... When using From URL the photo is not stored on the forums server... The photo is retrieved from photo bucket when the web page loads onto the screen... I will send you my email and we will see what damage the compression is doing... The pixels/dots per inch (PPI/DPI) also affects the size of the photo on or screens... If you could humor me try changing the PPI/DPI on your photos from 72 to 600 so that leaving the total pixels the same and letting the actual size change... Upload them again and see what we get... If we are not getting substantial data loss thru compression then I have some other ideas... Let me get you my email!!!

[ray_parkhurst]

Jim...the entire image is less sharp when resized by 1 pixel, not just one area. I just emailed you two files. One larger and with less compression, and one smaller with more compression. I'm not sure what you mean about changing the PPI/DPI settings. Those settings are not part of the image, they are only invoked with you try to print. Don't let that confuse the situation...Ray

[ray_parkhurst]

OK, so Jim and I completed the experiment. I emailed a larger, uncompressed file and a smaller, compressed one, and Jim mailed them back to me. They were exactly the same size and resolution as the originals. So it does not look like there is a general issue with the transmission. I also have done similar upload/download to Photobucket, and the file comes back the same. I think there is just some code in the forum software that modifies the file as it uploads it. This might be some sort of anti-piracy thing, so that the file can be distinguished from the original, or perhaps some other purpose.

Jim, somehow we need to fix this problem, since it is corrupting every photo uploaded to the site.

[ray_parkhurst]

Here are the two files...first is a 1296x864, with size 1792KB. This file is too big for the forum, so I do expect it will be resized or compressed in some way. The second is 648x432, size 192KB, so this one should fit within the forum limits.
143160
143161

[ray_parkhurst]

Wow! I just downloaded the 2 images, and the first one was resized, but the second one was not. So now the plot thickens. I thought I had been fitting within the forum limits on size, but indeed the images are either too large by pixel dimensions, or too large by file size.

Jim, what are the forum limits for max size by pixels, and max size by file size?

[ray_parkhurst]

Here is the largest pixel size image I seem to be able to make that is <300KB

143169

Edited to add: seems as long as you stay within 300KB, the forum software won't corrupt the file by making it 1 pixel smaller.

[jfines69]

Wow! I just downloaded the 2 images, and the first one was resized, but the second one was not. So now the plot thickens. I thought I had been fitting within the forum limits on size, but indeed the images are either too large by pixel dimensions, or too large by file size.

Jim, what are the forum limits for max size by pixels, and max size by file size?
Ray, When you are in Manage Attachments just above the Add Files button is a question mark... Click that and you get all the info for file types and the allowed sizes... .jpg and .jpeg are 585.9KB and 1680 x 1050... It use to be that if the file was to large in size or pixel dimensions it would be rejected... Now it appears to size the image down!!!

[jfines69]

Here is the largest pixel size image I seem to be able to make that is <300KB

143169

Edited to add: seems as long as you stay within 300KB, the forum software won't corrupt the file by making it 1 pixel smaller.
Do you still have issues with details???

[ray_parkhurst]

Do you still have issues with details???

For sure there are issues with sharpness when the image is resized by 1 pixel. Let's try this one...it's 583K:

143182

OK, it worked. I guess the files I was uploading were too big, and in the past I was relying on the forum software to tell me so. But the software now just resizes (and corrupts by shaving 1 pixel) the file without telling the user.

[VAB2013]

Thank you very much Ray and Jim for your research into this! I have been trying to follow along, but honestly... I am lost. Please tell us if you have determined how to post photos on the forum to avoid the forum software resizing it.

[ray_parkhurst]

Viv...the key is to make sure you fit within the size limits, and then it seems you will be OK. I'll try posting more and see if there are other situations that cause problems. Don't trust the forum software to tell you if the file is too big, as it won't.

[VAB2013]

Viv...the key is to make sure you fit within the size limits, and then it seems you will be OK. I'll try posting more and see if there are other situations that cause problems. Don't trust the forum software to tell you if the file is too big, as it won't.

Thank you Ray! So as long as the file size does not exceed 300KB then it should be okay?

[ray_parkhurst]

Thank you Ray! So as long as the file size does not exceed 300KB then it should be okay?

The size limit is 585.9KB, with resolution of 1680x1050. Odd sizes, but that's what the forum allows.

Weird thing is that I had uploaded a file that was smaller than this earlier, both file size and resolution, and it was corrupted by the forum. This is what really started the concern, but now when I upload within the limits, it seems OK. I am not sure why, so I can't say the problem is completely fixed just by fitting within the limits, but for sure it seems more likely. I do plan more experiments to see.

[VAB2013]

The size limit is 585.9KB, with resolution of 1680x1050. Odd sizes, but that's what the forum allows.

Weird thing is that I had uploaded a file that was smaller than this earlier, both file size and resolution, and it was corrupted by the forum. This is what really started the concern, but now when I upload within the limits, it seems OK. I am not sure why, so I can't say the problem is completely fixed just by fitting within the limits, but for sure it seems more likely. I do plan more experiments to see.

Thank you Ray! Your knowledge in researching this is greatly appreciated! We all want our photos to look as good as possible when we post them to the forum, especially after we have spent a great deal of time to get them in focus, etc.

[Maineman750]

Sorry I'm late for the party but it seems you have things mostly worked out.....on top of buying a new house, selling the old place, I was hit by the remnants of a tornado last week....PM notifications aren't reliable so the mods will have to make a phone call to Peter for issues like this.

[VAB2013]

Sorry I'm late for the party but it seems you have things mostly worked out.....on top of buying a new house, selling the old place, I was hit by the remnants of a tornado last week....PM notifications aren't reliable so the mods will have to make a phone call to Peter for issues like this.

Thank you Roger! Sorry to hear your new home was hit by remnants of a tornado! Hope you and the pups and your house are okay! Jim may have yours and Peter's phone numbers, but I do not.

[jfines69]

Sorry I'm late for the party but it seems you have things mostly worked out.....on top of buying a new house, selling the old place, I was hit by the remnants of a tornado last week....PM notifications aren't reliable so the mods will have to make a phone call to Peter for issues like this.
We were trying to work it out before calling the big guy... I believe it is all squared away???