Qimage downsizing/interpolation... :-(

Downloaded a Qimage trial. Thought this would be the one for my needs. I will do a lot of batch downsizing using different kinds of interpolation such as lanczos & mitchell. To downsize in Qimage I double click an image, go to queue/batch filter and puch the interpolation method button. There I put all settings to maximum and set "final print sharpening" to "off" (I want to do all the sharpning and other processing in PS). Pressing apply one can check the results & they were really dissapointing. Welcome to jaggie heaven. I've tried other programs that use lanczos and they do not produce these results. The results are nearly or just as bad as in in "pixel resize" mode and much worse than the results i get in PS7 using the bicubic method. All of the methods look alot_sharper in Qimage though. Could it be Qimage adding some weird sharpening although I've set "final print sharpening" to "off"? Any ideas appreciated...

Thanks in advance

Mikael
Canon PowerShot G2
http://www.pbase.com/mikael

Mikael,

I have no experience with QImage, but possibly the Lanczos and other methods are improperly implemented for reduction. Reductions should involve convolution kernels with support dimensions that are inversely proportional to the reduction scale factor, whereas enlargements, rotations, and translations should use fixed support size. For example, Lanczos 2 should use a 4x4 pixel kernel for all enlargements, but should be implemented with an 8x8 kernel for 1/2 reduction, 16x16 for 1/4 scale, etc. When a kernel designed for enlargements is used to make a reduction, jagged lines can result. When an enlargement kernel is used to make reductions, the greater the reduction, the more jagged the lines will be. This applies to other convolution based scaling methods as well. That said, I find it very hard to believe that the author of QImage doesn't know this.

Mikael said:

Downloaded a Qimage trial. Thought this would be the one for my
needs. I will do a lot of batch downsizing using different kinds of
interpolation such as lanczos & mitchell. To downsize in Qimage I
double click an image, go to queue/batch filter and puch the
interpolation method button. There I put all settings to maximum
and set "final print sharpening" to "off" (I want to do all the
sharpning and other processing in PS). Pressing apply one can check
the results & they were really dissapointing. Welcome to jaggie
heaven. I've tried other programs that use lanczos and they do
not produce these results. The results are nearly or just as bad
as in in "pixel resize" mode and much worse than the results i get
in PS7 using the bicubic method. All of the methods look
alot_sharper in Qimage though. Could it be Qimage adding some
weird sharpening although I've set "final print sharpening" to
"off"? Any ideas appreciated...

Thanks in advance

Mikael
Canon PowerShot G2
http://www.pbase.com/mikael

Click to expand...

Mikael said:

. Could it be Qimage adding some
weird sharpening although I've set "final print sharpening" to
"off"? Any ideas appreciated...

Click to expand...

No that would not be it. If you tell it not to sharpen it will not. However, that final sharpen isn't a bad idea. The theory is that when you reduce the image size for printing, you need to get one final sharpen to make it look good. That final print sharpen will do that for you without over sharpening the image.

I don't fully understand what you are doing. You are doing batch resizing in Qimage? For printing or are you saving the images?

As for the jaggies, I took a fairly large image and reduced it down to about 100x100 and there were a lot of jaggies in it. More than I think there should be, but I didn't actually make a print of the image, so it might just be in the display version.

Serra said:

Mikael said:

. Could it be Qimage adding some
weird sharpening although I've set "final print sharpening" to
"off"? Any ideas appreciated...

Click to expand...

No that would not be it. If you tell it not to sharpen it will
not. However, that final sharpen isn't a bad idea. The theory is
that when you reduce the image size for printing, you need to get
one final sharpen to make it look good. That final print sharpen
will do that for you without over sharpening the image.

I don't fully understand what you are doing. You are doing batch
resizing in Qimage? For printing or are you saving the images?

As for the jaggies, I took a fairly large image and reduced it down
to about 100x100 and there were a lot of jaggies in it. More than
I think there should be, but I didn't actually make a print of the
image, so it might just be in the display version.

Click to expand...

Yes. I'm trying to batch downsize for onscreen use. Not for printing, and it's not looking too good. After trying all of the methods (which some I thought should blur the image) it seems like they kind of sharpen the image. They all look alot sharper than the 2 mp input zoomed too 100%, and the jaggies are terrible. I know final sharpening ain't bad. I always do it after downsizing in PS7, but with KPT Equalizer which i think is the best sharpener after trying every sharpener available (including the much more expensive nik). If you have tips on any other program that could do this better, please help.

Mikael
Canon PowerShot G2
http://www.pbase.com/mikael

Mikael,

Qimage is by far the best. It takes a while to get used to it. E-mail Mike
with your doubts.

Raul

Mikael said:

Downloaded a Qimage trial. Thought this would be the one for my
needs. I will do a lot of batch downsizing using different kinds of
interpolation such as lanczos & mitchell. To downsize in Qimage I
double click an image, go to queue/batch filter and puch the
interpolation method button. There I put all settings to maximum
and set "final print sharpening" to "off" (I want to do all the
sharpning and other processing in PS). Pressing apply one can check
the results & they were really dissapointing. Welcome to jaggie
heaven. I've tried other programs that use lanczos and they do
not produce these results. The results are nearly or just as bad
as in in "pixel resize" mode and much worse than the results i get
in PS7 using the bicubic method. All of the methods look
alot_sharper in Qimage though. Could it be Qimage adding some
weird sharpening although I've set "final print sharpening" to
"off"? Any ideas appreciated...

Thanks in advance

Mikael
Canon PowerShot G2
http://www.pbase.com/mikael

Click to expand...

Raul said:

Mikael,

Qimage is by far the best. It takes a while to get used to it.
E-mail Mike
with your doubts.

Raul

Click to expand...

Hmm, I've sent him mail three times, and I've got reply. Guess I'll send him one more. What other programs have you used for downsizing using these interpolations when saying this one is by far the best?

Mikael
Canon PowerShot G2
http://www.pbase.com/mikael

Raul said:

Qimage is by far the best. It takes a while to get used to it.
E-mail Mike

Click to expand...

I have to wonder about that statement. I really like QImage and I would give it a huge thumbs up in just about every area, but I really don't think it is an area where QImage is at its best.

Mikael said:

What other programs have you used for downsizing
using these interpolations when saying this one is by far the best?

Click to expand...

Actually, I've never seen them in another program, so by default, Qimage must be the best.

However, it does seem like you wouldn't need fancy interpolation for downsizing. In fact, as you are reducing the number of pixels, all you really need to do is avoid jaggies and you should be fine, so any method that reduces without causing jaggies would be fine.

I might be wrong, I'm not an expert, but it seems like interpolation is MUCH more important when you are upsizing.

Given that, the best method for downsizing would be to use a step method, like Fred's Stair Interpolation, but in reverse. Down size in several steps in Photoshop. Do the downsizing in an action that steps down in 5 or 6 smaller steps.

I use Qimage to "upsizing" for printing, and it works great. I have been using the save feature to create a file with the changes and then burning to a cd for printing at Walmart. I am very happy with the results.

I would suggest using Irfranview ( freeware) that has the ability to resize multiple files using the batch coversion. I typically resize at 800x600 for viewing on web or sending by e-mail. It is quick, simple, with good results.

Also, Thumber will resize, create a thumbnail, and a web page all in one operation of a set of files. I use this program normally when I am posting a web page with my photos for family, etc.

Jeff

Mikael said:

Downloaded a Qimage trial. Thought this would be the one for my
needs. I will do a lot of batch downsizing using different kinds of
interpolation such as lanczos & mitchell. To downsize in Qimage I
double click an image, go to queue/batch filter and puch the
interpolation method button. There I put all settings to maximum
and set "final print sharpening" to "off" (I want to do all the
sharpning and other processing in PS). Pressing apply one can check
the results & they were really dissapointing. Welcome to jaggie
heaven. I've tried other programs that use lanczos and they do
not produce these results. The results are nearly or just as bad
as in in "pixel resize" mode and much worse than the results i get
in PS7 using the bicubic method. All of the methods look
alot_sharper in Qimage though. Could it be Qimage adding some
weird sharpening although I've set "final print sharpening" to
"off"? Any ideas appreciated...

Thanks in advance

Mikael
Canon PowerShot G2
http://www.pbase.com/mikael

Click to expand...