1.96.5, pic resize does not reduce the file size, in the opposite

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visionhelp
Posts: 16
Joined: Mon Jan 09, 2017 5:42 pm

1.96.5, pic resize does not reduce the file size, in the opposite

Postby visionhelp » Wed May 03, 2017 2:43 pm

Hi,

I want to reduce the file size of a pic with reducing the ´Changing Size´ of a pic.
Under ´New Calculate´ is:
Lanczos, Bi-Lenear, next neighbour and so on switchable, but which I cannot try out all, with the possibility, this does not help.

I use Lanczos, reduce to 50 %, and the file grows from 60 Kb (100 %) to 80 Kb (50 %), f. e.

Thanks for help.
Last edited by visionhelp on Wed May 03, 2017 9:18 pm, edited 3 times in total.

cday
XnThusiast
Posts: 1508
Joined: Sun Apr 29, 2012 9:45 am
Location: Cheltenham, U.K.

Re: 1.96.5, pic resize does not reduce the file size, in opposite

Postby cday » Wed May 03, 2017 3:09 pm

You wish to reduce the file size of an image?

If you are using Image > Resize... that function provides a way to change the pixel dimensions ('canvas size') of an image, and if you reduce the pixel dimensions the file size will be reduced, other things being equal, particularly the compression method and settings when the image is resaved. I don't think that the resampling method you select will affect the file size of the resulting image.

If you simply wish to reduce the file size of an image, you could experiment with opening the file and then resaving it with higher compression, and also consider whether saving to a different file format might be better.

If you wish to easily experiment with saving with different compression levels and file formats, and file formats, the function File > Export... may provide an easy way to do that.

visionhelp
Posts: 16
Joined: Mon Jan 09, 2017 5:42 pm

Re: 1.96.5, pic resize does not reduce the file size, in opposite

Postby visionhelp » Wed May 03, 2017 3:29 pm

Thanks for this very fast answer.

Convert from jpg to ... ? To reduce ?

Under "Image" there are 14 points to select.
One is ´DPI set´.
One is ´Size change´. (This is what I use.)

"pixel dimensions ('canvas size') of an image", in german, I cannot find.


"resaving it with higher compression": with file EXPORT ... :
´Export´ sounds disconcerting to me, but with different compressions possible it sounds it is worth some tries.


Sorry, translated Canvas: ´Size change´ is ´Canvas size´ change.
No, sorry again, there is ´Canvas size change´and ´Size change´.
I begin with this.


Thank You very much.

cday
XnThusiast
Posts: 1508
Joined: Sun Apr 29, 2012 9:45 am
Location: Cheltenham, U.K.

Re: 1.96.5, pic resize does not reduce the file size, in opposite

Postby cday » Wed May 03, 2017 3:48 pm

The basic question is whether you wish to reduce the image filesize by modifying the image itself, principally by changing the pixel dimensions, or whether you wish to simply reduce the files size by increasing the compression or saving to a different file format, if there is a more suitable format, considering any possible reduction in quality.

In the Image > Resize... window the pixel dimensions can be changed (either by a percentage value or by entering new pixel dimensions) here:


Image_1.png
Image_1.png (16.21 KiB) Viewed 207 times


Edit:

If you wish to make a web photo album, you may well wish to reduce the pixel dimensions of your images as a first step, but I'm not the best person to advise you on suitable dimensions...

visionhelp
Posts: 16
Joined: Mon Jan 09, 2017 5:42 pm

Re: 1.96.5, pic resize does not reduce the file size, in opposite

Postby visionhelp » Wed May 03, 2017 7:47 pm

"principally by changing the pixel dimensions":

It appears a little bit mixed up.

I am coming from this side:
To reduce the image size means for me, to reduce Width and Height.
(Seeing this, new for me, Units, which I cannot understand what that means, makes me notice, that there is a newer version of XnView than my actually.)

But when reducing Width and Height to, f. e., about 50 %, but the result of the file-size is bigger than before, than, where is the reducing of the file ?

Perhaps this question does make clear, what I mean.

There is Image Resize and Canvas Resize, if still.
What You say from, I understand Image Resize as Compression Resize, and Canvas Resize to reduce, or make bigger, too, Width and Height.

And now the mixed up, I began with:
If in Image Resize a change of Width and Height is possible, too, how can it be possible to understand this precise distinction first once at all ?

cday
XnThusiast
Posts: 1508
Joined: Sun Apr 29, 2012 9:45 am
Location: Cheltenham, U.K.

Re: 1.96.5, pic resize does not reduce the file size, in opposite

Postby cday » Wed May 03, 2017 8:41 pm

visionhelp wrote:To reduce the image size means for me, to reduce Width and Height.

Yes, to reduce the image width and height measured in pixels, which you can do using Image > Resize... : you can either set say 50% and 50%, or specify new pixel dimensions, using the drop-down list setting.

But when reducing Width and Height to, f. e., about 50 %, the result of the file-size is bigger than before... then, where is the reducing of the file ?

The likely reason the file size is increased is that the file is being resaved with lower compression than the original file, you can set the compression value used in the File > Save As... 'Options' dialog.

... then, where is the reducing of the file?

The resize is in the *pixel dimensions* of the image.

There is Image Resize and Canvas Resize...

Canvas size... is a different function, which can cause confusion, and I can't immediately provide a clear explanation of the difference, but above I used 'canvas size' to refer to the pixel dimensions of the image you were processing, and suggested using the Canvas resize... function.

I hope that's clearer, you can reduce file size either by reducing the pixel dimensions, or by saving with higher compression.

If you're looking to place photographs, for example, in a web photo album as JPEGs, you may be able to reduce the original pixel dimensions, and also increase the compression level, considerably with little or no visable loss of quality, if you experiment a bit.

visionhelp
Posts: 16
Joined: Mon Jan 09, 2017 5:42 pm

Re: 1.96.5, pic resize does not reduce the file size, in opposite

Postby visionhelp » Wed May 03, 2017 9:08 pm

Thanks for the effort.

"saving with higher compression":

I forgot to note, that files about 800 Kb, with reducing Image Resize to 50 %, comes to about 120 Kb, regularly, without changing anything, no compression changes, no extension changes. (Not Canvas Resize.)

This would have been important to say at once, sorry.

Only pics at about 60, 80 Kb, reducing to 50 % f.e., lead to his results of the bigger file-sizes than the 100 % ones.


"you may be able to reduce the original pixel dimensions, and also increase the compression level, considerably with little or no visable loss of quality, if you experiment a bit.":
Yes. Much work. An other theme. But is not the point here, I think.


I took just a fast view to:
Batch Processing - Format - Options - Write - JPEG: there are so many things to set possible ...
Attachments
Batch Processing - Options - Common - Read_Write - Write - JPEG.jpg
Batch Processing - Options - Common - Read_Write - Write - JPEG.jpg (129.15 KiB) Viewed 181 times


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