JPEG Compression??

[whitpet]

I'm running PSPX3. I'd appreciate some help understanding the effect of no compression (or compression factor = 1) on saving files. I've searched thru the Help files, but they really don't address compression in detail.

I've got a JPEG image file straight from my camera that's approximately 4.1MB in size. If I do nothing else but "Save As" with a compression factor of 1, the new file size is approximately 50% larger, or 6.2MB. What has changed to make the file size larger? Both images are still 72DPI, 3648X2736px. I can't image that I have done anything to "improve" image quality, so why did the file size increase? Thanks for your help.

[flagpole]

a compression factor of 1 is not the same as no compression. uncompressed that image would be approximately 30megabytes

jpeg uses some very clever maths to make image files smaller, even on maximum quality it is, in this case, one 5th the actual size.

if you have done nothing to the image then don't save it, just use the original. if you have done something to the image then you have to make a decision about the quality you want v the file size. you can use the jpeg optimizer to do this it will allow you to try different quality levels and see the results and file size. if you like the original files and you've just change the colour and contrast a little then you might wont to try adjusting it until the output is about 4MB.

jpeg is a lossy process, so each time you open an image and save it again you will lose some quality. strangely even if you save an image with a compression value of 99 making a very small file, if you open it again and save it with a compression value of 1 the file will be large again. which is what is happening with your camera. it may be using an equivalent compression value of say 2 or 3

on x3 i used to use a default value of 5 i think. but i would frequently change it depending on what i wanted to use it for,

[LeviFiction]

Just a quick add here, you can change the encoding type to lossless.

[LindaSue]

Just a quick add here, you can change the encoding type to lossless.

Unless they've changed something since PSPX2, the problem with using the Lossless JPG option is that other programs might not be able to open them. I just saved one with PSPX2 and IrfanView can't open it. Also, Windows XP can't create a thumbnail for it when I view it in Explorer. My CompuPic image viewer can't open it either. Neither can Serif's PagePlus. Apparently those files can only be opened by PSP itself which makes that format rather useless.

[39_Steps]

When I first opened the Irfanview browser to the folder containing the newly saved "lossless" JPG, the file did not appear. Then I opened Windows Explorer, went to the lossless.JPG file and clicked on "Open with". From that point on the file was not only visible in the Irfanview folder, but opened in all other Photo Editing apps that I have on my Vista laptop.

Perhaps is is a file association problem, or an indexing issue that takes a couple of iterations to work itself out the first time. PSP X4.

[LindaSue]

When I first opened the Irfanview browser to the folder containing the newly saved "lossless" JPG, the file did not appear. Then I opened Windows Explorer, went to the lossless.JPG file and clicked on "Open with". From that point on the file was not only visible in the Irfanview folder, but opened in all other Photo Editing apps that I have on my Vista laptop.

Perhaps is is a file association problem, or an indexing issue that takes a couple of iterations to work itself out the first time. PSP X4.

I don't have that option under "Open with" on Windows XP. Is there a way to add lossless JPG to the list? I really don't see much point in using that format though. If I were to post one on my website most people wouldn't see the picture unless they've got their computer configured to view them.

[flagpole]

When I first opened the Irfanview browser to the folder containing the newly saved "lossless" JPG, the file did not appear. Then I opened Windows Explorer, went to the lossless.JPG file and clicked on "Open with". From that point on the file was not only visible in the Irfanview folder, but opened in all other Photo Editing apps that I have on my Vista laptop.

Perhaps is is a file association problem, or an indexing issue that takes a couple of iterations to work itself out the first time. PSP X4.

I don't have that option under "Open with" on Windows XP. Is there a way to add lossless JPG to the list? I really don't see much point in using that format though. If I were to post one on my website most people wouldn't see the picture unless they've got their computer configured to view them.

if you hold down shift and right click you should have the open with option... IIRC

[teknisyan]

0 compression would mean is the same for raw files from digital camera. You can save a PspImage file with or without compression. Both compression methods that Corel PaintShop Photo Pro uses are lossless and reduce the file size without losing any image information. Uncompressed files require more disk space.

Corel PaintShop Photo Pro uses the following compression methods:
• Run length encoding (RLE) — a fast compression method, which compresses most multilayer images to about 75 percent of their original size. This method works well with images that contain large areas of the same color.
• LZ77 compression — a slower compression method that compresses most images to smaller sizes than with the RLE method. This method works well with photorealistic images.

You can also follow these steps to save a Jpeg (*.jpg) and keep the high-quality of the photo: http://corel.force.com/index/articles/e ... -the-photo

[LindaSue]

When I first opened the Irfanview browser to the folder containing the newly saved "lossless" JPG, the file did not appear. Then I opened Windows Explorer, went to the lossless.JPG file and clicked on "Open with". From that point on the file was not only visible in the Irfanview folder, but opened in all other Photo Editing apps that I have on my Vista laptop.

Perhaps is is a file association problem, or an indexing issue that takes a couple of iterations to work itself out the first time. PSP X4.

I don't have that option under "Open with" on Windows XP. Is there a way to add lossless JPG to the list? I really don't see much point in using that format though. If I were to post one on my website most people wouldn't see the picture unless they've got their computer configured to view them.

if you hold down shift and right click you should have the open with option... IIRC

I tried all of the options listed in the right-click Open menu and it won't open in any of them except PSP. Maybe it's an XP issue or maybe only lossless JPGs saved with X3 and X4 will open in other programs. The ones created with PSP8 and X2 won't.

[flagpole]

i'm reasonable familiar with the jpeg standards and i'd never heard of lossless jpeg. but when i use it windows creates thumbnails they even open in MS paint. and examination of the file reveals nothing different about them.

best i can tell is that the lossy steps such as DCT are effectively removed from the process but the file remains fully compliant jpeg.

[LindaSue]

i'm reasonable familiar with the jpeg standards and i'd never heard of lossless jpeg. but when i use it windows creates thumbnails they even open in MS paint. and examination of the file reveals nothing different about them.

best i can tell is that the lossy steps such as DCT are effectively removed from the process but the file remains fully compliant jpeg.

It must be a Windows XP problem then. XP must not support lossless JPG.

[LindaSue]

The reason I was interested in using Lossless JPG is that I thought it would be a good way to avoid the green dots that PSP8 adds to all JPGs. It does solve that problem but it's useless to me if I can't open or view my images in any program other than PSP. I did find another solution though. I can use Progressive JPG with PSP8 and it doesn't put any green dots on my images. I can see where the dots would be but they're the same color as the rest of the picture so they don't stand out like the green dots do. As a small bonus, the Progressive JPG files seem to be slightly smaller than standard JPG with both set to a compression of "1". The lossless JPGs were about three times the size and are even larger than PNGs.

[JRosenfeld]

i'm reasonable familiar with the jpeg standards and i'd never heard of lossless jpeg. but when i use it windows creates thumbnails they even open in MS paint. and examination of the file reveals nothing different about them.

best i can tell is that the lossy steps such as DCT are effectively removed from the process but the file remains fully compliant jpeg.

It must be a Windows XP problem then. XP must not support lossless JPG.

Not an XP problem: I run XP pro SP3 and have no problems viewing lossless jpg created in PSP X4, on my PC. Thumbnail is created and shows in Windows Explorer, Windows Picture and fax viewer ('preview' on right click menu on my system) shows it and opening the file in other apps also causes no problem (e.g. Paint, MS Word 2002, Roxio Photosuite all open the file; to select one or other software you have: right click, open with, if the app is not listed click Choose program, browse to its .exe file, click OK).

As test file I used a 3872 x 2592 pixel, 300dpi .jpg from a Nikon camera D40X (not mine, just a photo someone sent me, so I don't have the RAW file) file size 2,612 KB.

I opened that in PSPX4 file/save as, selected jpg, in options selected lossless, and saved under a different name. This file was 6,210 KB

I also tried a few other pictures including starting with other formats (e.g. png)

[LindaSue]

I don't have PSPX4 but the Lossless JPGs created with PSP8 and X2 can't be viewed in anything other than PSP. They must have changed something since X2. JRosenfeld, can you post a sample of one here so that I can see if any of my programs can view it?

[flagpole]

I don't have PSPX4 but the Lossless JPGs created with PSP8 and X2 can't be viewed in anything other than PSP. They must have changed something since X2. JRosenfeld, can you post a sample of one here so that I can see if any of my programs can view it?

here. lovely summer glau.

it's not me in the picture btw, just something i found on t'internet.

edit you have to actually click the image to get the lossless version. which means the forum software can handle the images correctly.

also the exif data says psp14.00 not 14.01