Image Conversion -> Bad Quality

Hi all,

since the mailinglist died, I have the impression, that
the traffic regarding different topics has somewhat
reduced.. or is it just me.. ?!..

Well, on to my topic..

As I was one of these guys wishing for an integrated
image conversion tool, I make use of this new feature in
v8, BUT.. the quality of JPGs is more than bad.

As an example:
I have a JPG from my DigiCam 1024x768 ~ 240KB.

Now I convert this image to 50% quality and size of
800x600. The resulting picture looks ugly with big
artefacts and is big in size also.. ~110KB.

Now I use IrfanView to do the same conversion,
the picture has much, much less artefacts and its size
has reduced to about ~50KB.
Thats what it should be like.

The image is half the size and doubles the quality in
camparison to the DO conversion.
So I do not use the DO functionality anymore, it's quite
useless, as I don't want my pictures big in size and
small in quality.. 8(

Perhaps there's something I do wrong,
or anyone has any idea about this..


As with all things JPEG it depends a lot on your source image as to the result you get when you resave it. But as Opus just uses standard JPEG code, the same JPEG code that almost every other program uses, I would be surprised if it was that different.

I think the crucial piece of information you are leaving out is that IrfanView actually has a resample option as well as a plain resize option. Resampling will almost always give you better results than resizing, and so given this it is probably not surprising that IrfanView gives better results. Opus doesn't claim nor try to be a fully fledged image manipulation tool. The Image Conversion function is a quick and simple way of performing common conversion tasks, nothing more.

Having said that, here are some sample pictures:

The original, 1024 x 768, 168 KB:

Resized in Opus to 800 x 600, 50% quality, 84 KB:

Resized in ACDSee, 106KB:

Resized in IrfanView, 81KB:

Resampled in IrfanView, 74KB:

Now to my admittedly untrained eye, there's very little difference between the four resized images. The resampled IrfanView image is the best, but I would say the resized IrfanView image is actually the worse. I can't pick it between Opus and ACDSee but Opus produced a file over 20K smaller. (I'm not taking any credit for this - Opus and ACDSee use exactly the same jpeg library, the difference is probably down to the default settings used).

Having said all that, if you find IrfanView gives you better results, please feel free to continue using it :slight_smile:

Sorry, for digging this.. but for anyone ever reading this thread,
I wanted to add following information.

The DO image conversion works just fine, It just does not extract/remove the
exif-thumbnail, so there is always a quality drawback, if you want to have
a picture with 800x600 to be the same file-size as one picture reduced in size
by Irfanview. Irfanview uses the 20-30kb for image-data, whereas DO
has to save the jpg in much less quality to achive same file-size, because
the exif-thumbnail may still reside within the picture..

You get the picture ?!.. o)

I just use nconvert.exe to strip jpgs from unnessassary exif thumbs now.
Would be cool if you had the option within the DO image-conversion dialog.