Resizing pictures

[Jerry S.]

Greetings, I could use some suggestions. I took many sports action photos in HQ mode on my digital camera. The photos are in the 450 KB range except for a few non-action shots in a higher resolution mode at about 1100 KB each. I'd like to reduce them to about 100 KB for my computer slideshows.

How should I lower the sports action photos down from 1000 KB and 450 KB to about 100 KB? I have IrfanView and have messed with the batch file settings. It appears I would have to lower the "quality" slider to get them to compress down to 100 KB. Will the quality be fine for computer slideshows still once the photos are reduced? This should help people with older computers so they don't have any problems due to large file sizes and lack of memory or processor speed. I will have a few mp3 music files playing also.

The reason I used the middle range high quality setting was so I could give people the option of printing some of them at maybe 5 by 7 or a little smaller and have reasonably good quality prints (I haven't tested this theory yet by printing any). Any thoughts or suggestions? Jerry S

[hotmetal]

Hi there,

Do you have any image editing software such as Paint Shop Pro or Photoshop?

If so you could resuze the image to 1024 * ??? pixels and save as a mid range jpeg. this would preserve your original and produce a more usable file for pte.

Alan

[SilverSurfer]

Hello,

I have found image quality to be good on a comp using JPEG compression at 95% quality.

You may also consider making the image have a lower DPI (dots per sqaure inch). This will reduce the dimension size of your image. 72 or 96 DPI should be fine for viewing on a comp. You want 300 DPI for printing.

I don't reccemend using TIF or BMP. These formats are large in file size. Only use them if you want the data of every pixel preserved, which you probably don't need. Only use GIF if your image has only 256 colors. You may find PING to be good for what you need. Its sort of an alternative to GIF, but for true color images. It supports 16, 24, and 32 bit color very well.

General rule of thumb for me is, I always use JPEG at 95% quality. You can make the image a bit smaller without compromising quality by much using a Progressive JPEG.

IrfanView supports all the image formats mentioned.

SilverSurfer

[Ken Cox]

irfanview will resize quite easily

http://irfanview.tuwien.ac.at/

and make sure you get the plugins as well

ken

[JRR]

Here is my two cents worth....

Virtually all my shows use "FADE" as the transition between images. This is a very intensive process for a computer. As some of my shows are shown on computers of various vintages and horsepower, I use PhotoShop to reduce the images to 800x600 and save them as jpg quality 6.

While the images might be a little smaller than some might like, I can be confident that the show will work smoothly on most (not all) computers.

If you are not using FADE, it is amazing how large an image (and show size) even older computers can handle in PTE. An example: One show I have that uses essentially only CUTS runs beautifully on a firend's computer that immediately freezes with a short show with slow FADES.

Jim

[alrobin]

irfanview will resize quite easily

Ken,

It's worth pointing out, though, that if you want the same quality of jpeg in IrfanView as you would have for the same % quality compression as you would have obtain with Photoshop, you have to set the % at a higher value in IrfanView. It seems to compress down more than Photoshop for the same % designation.

[LumenLux]

I like Irfanview a lot. It is my emotional favorite. That said, I was surprised with a recent experience. I had a group of digital originals 2304x1704, about 1500k average. I was downsizing them with Irfanview to be 50-100 K. I don't remember exact dimensions, but about 400x600 & 800x600. I was setting Irfanview jpg "quality" to 60. The result, on some photos, was visually apparent and somewhat displeasing. In an effort to improve results with same size output, I tried Photo Elements 2 with the "Save for web" option. I was amazed at the better pictures that resulted. I think perhaps Guido recently made some favorable reference to this "Save for web" option. I don't know if it uses some new smarter algorythm or what. But in at least my most recent use, it was impressive. If anyone else can share experience or shed light on this observation, I would certainly be interested.

[alrobin]

I found in some recent tests that I had to set the compression at 30 in IrfanView to obtain the same quality, and same image file size, as for a quality-10 jpeg compression in Photoshop.

[think(box)]

Looks like everyone has answered Jerry's question fairly well. You can generally bring your pictures down to between 30KB and 200KB depending upon just how "high-res" your photos are, how "high-res" you want to display them on your computer monitor and how much space for the show. I have a display performance finding to include:

If you set your PC monitor screen area to 1024x768 and find that fades are jumpy, try using 800x600 monitor screen area setting. Each painted frame at 24-bit color setting involves about 2.25MB of screen data at 1024x768 screen area display. Screen data is only 1.37MB at 800x600 screen area display. The CPU workload decreases by about 40% for 800x600 screen setting. This can help and won't cost the non-perfectionist viewer too much in lost viewing resolution.

In "light" of Al and Bob's previous three replies about visible image quality here is a general forum question:

I have used dozens of photo app's that can compress for JPEG files. I have yet to find any that match Adobe's tools for file compactness at a given visible photo quality, and hence that match Adobe's compression goodness. Adobe is fairly kind to us in that their software compresses just as well whether it is a bundled product like PhotoDeluxe Business Edition, or a paid product like Photoshop Elements or the best, Photoshop itself. It was nice of Adobe to not water-down the compression goodness in low-end products the way they do their general feature set and user interface.

I'm sure many of us have compared compression "goodness" between photo processing app's, that is "the ability to get the same visible image quality in the smallest possible JPEG file size". Please share your comparison results! I have downloaded Irfanview, but haven't yet made this comparison. Al says it matches Photoshop and we know many are using it. What app's are the best, using Adobe as a comparison metric? Are there any that are even close to Photoshop and Irfanview? Thank you for sharing your findings!

Cheers,

[Guest guru]

Hi all!

I never made a serious comparison between Photoshop and all other softwares about the compression/quality or quality/size ratios. But I totally agree with Bob Lumenlux: I can say my Jpeg saved "for Web" by Photoshop have an outstanding quality/size ratio, even because I can compare in real time the result with the original picture (I don't like very much the batch conversions).

For the moment, only two little remarks.

SilverSurfer:

DPI are at all meaningless in pictures quality. They are significant only when you print the picture (and you can always set DPI as you want). This means simply that an 800 x 600 dpi image can be printed at 8 x 6" size @ 100 dpi, at 800 x 600" @ 1 dpi, at 4/5 x 3/5" @ 1000 dpi and so on.

Think(box):

You're right when you say the "CPU workload decreases by about 40%" from 1024 x 768 to 800 x 600. But consider the additional CPU work if you look a 1024 slideshow with a screen resolution of 800 x 600, since PTE must also resize the pictures!

[Tripstrilles]

@Guru

Yes you are right. For my last show I have used the compression rate of 80 % with Photo Impact. The size of the images is 1024 x 768 horiz. and ??? x 768 vertical. I have test to view the show with 80 % screen-size and with image-size of 800 x 600 pixel.

On my old notebook with P II 233 MHZ there was no problem with the version of resizing to 80 %. The show runs well.

So I will use in future the resizing mode, so I can quickly change the show for every screen resolution 1024 x 768 and smaller. I hope I have time to upload it to beechbrook, but first I have to make it much smaller, because the size is about 100 MB with music.

Greetings, T.

[Michel]

Each painted frame at 24-bit color setting involves about 2.25MB of screen data at 1024x768 screen area display. Screen data is only 1.37MB at 800x600 screen area display. The CPU workload decreases by about 40% for 800x600 screen setting

I don't agree:

1024x768 or 800x600 is not the problem.

The problem is: 1.37 mb to 2.25 mb

When the the "CPU" open a 2.25 mb picture, the work is more important that for open 1.37 mb.

It's only this factor for me.

[think(box)]

Wow! A lot of input about this. I was confused after reading it and wondered how well I really understood the performance metrics. The only way to answer this for me was to make measurements that map out all cases and analyze the results. To do this I started with a set of 800x600 original size, 24bit color photo JPEGs and made a comparison duplicate set of same photos resized to 1024x768 and unsharp-masked to increase detail before saving. All were saved at Photoshop's 10 on a scale of 12 quality. Then I made four test shows in PTE, splitting by resolution in JPEG file (only 800x600 or only 1024x768 test sets) and by doing "Fit to screen" or not doing "Fit to screen" in PTE screen tab checkbox. I created the four shows with no transition effects so transition is immediate, and measured how many pictures per minute were displayed by the created P2E shows at three different screen area monitor settings, 800x600 (4:3), 1024x768 (4:3) and 1280x1024 (5:4 ratio FYI). I then created the four shows with 1 second simple fading transition between pictures to test fading smoothness. I used PTE V4.01 for all shows.

I have one special PTE finding noted in results with an asterisk (*): When an image is too large to fit on screen, P2E show software reduces it to fit whether or not I check the box "Fit to screen". This is an inconsistent P2E function but clearly the right way for shows to work. If reduction of oversized pic's wasn't unconditional then a picture larger than screen would display as a blown-up fraction of pic when we do not check the box, "Fit to screen". P2E performs correctly, but in considering performance measurements sometimes image is resized even though "Fit to screen" is not checked.

File size info:

The 800x600 photos average 130KB in JPEG file size

The 1024x768 photos average 245KB in JPEG file size

Test shows, key: 800x600 JPEGs not F.T.S., then "Fit to screen", 1024x768 JPEGs not F.T.S., then "Fit to screen"

Without fading, key: Pictures displayed per minute on a 400MHz P2 system used for all measurements

1 second fading, key: SF=smooth, RF=getting jumpy (visible screen repainting), JF=very jumpy (worst)

800x600 display, 24bit color (480,000 pixels, 1.37MB bitmap to paint full screen):

180 SF --- 180 SF --- 120* SF --- 120 SF

1024x768 display, 24bit color (786,432 pixels, 2.25MB bitmap to paint full screen):

177 SF --- 147 RF --- 129 RF --- 129 RF

1280x1028 display, 24bit color (1,310,720 pixels, 3.75MB bitmap to paint full screen):

171 SF --- 117 JF --- 141 RF --- 93 JF

Analysis:

Michel - you are correct in that JPEG image size is important, but it is not the only factor. JPEG image size dictates display time performance as it relates to decompressed JPEG bitmap size, at least in terms of non-faded pictures displayed per minute. Pixels in JPEG content relate very closely to image display bitmap formation time. The relationship pixels to time is close to proportional. If I understand correctly, Tripstrilles has found the same result. However I had made the remark about decompressed bitmap size in reference to fading jumpiness:

If you set your PC monitor screen area to 1024x768 and find that fades are jumpy, try using 800x600 monitor screen area setting.  Each painted frame at 24-bit color setting involves about 2.25MB of screen data at 1024x768 screen area display. Screen data is only 1.37MB at 800x600 screen area display. The CPU workload decreases by about 40% for 800x600 screen setting. This can help and won't cost the non-perfectionist viewer too much in lost viewing resolution.

Test results show that P2E forms a bitmap for a picture only once before displaying it, as is sensible. Then for image fading the screen area setting and percentage of screen filled by image indeed are the only two things that matter to fade jumpiness, along with computer speed of course. So for an image that fills the screen it is correct that fading "jumpiness" is less at smaller display monitor screen area settings.

Guido (guru) - you are correct in that performance suffers a little when P2E has to reduce, and more significantly when P2E has to enlarge. P2E's size-change quality is legendary, although that's another story.

In conclusion, the higher your screen area setting and screen percentage used, the more performance you need from the system to do unjumpy simple fade effects. Further, the larger your JPEG image is, and the higher your screen area setting and screen percentage used, the more performance you need from the system to display images at a high rate per minute. Given consideration of this by a show creator, PTE can make shows that play almost the same for everyone on any machine. That is really cool.

Thanks go out to all for input on this question.

Cheers!

[LumenLux]

Good work Bill. Thanks.

[Jerry S.]

I really appreciate everyone's input. I plan to test out Photoshop as an alternative to IrfanView. I'll also keep in mind lowering the screen resolutiion if the slideshow gets jumpy.

[Guest guru]

I too thank you very much, Bill, for your attentive and meticulous analysis, that is really useful to all PTE users.