Large JPG file after resize with nconvert

[Guest]

Excuse Me , I have some problem about nconvert.
I Use The Command .
nconvert -ratio -resize 400 0 PICT0001.JPG
after resize the image ,I also use IrfanView(Picture software) to resize The same picture
the result is

source PICT0001.JPG File Size : 970KB
use nconvert resize PICT0001.JPG :File Size : 119KB
use IrfanView resize PICT0001.JPG : File Size : 30KB

so I don't Why come to the result ? Thanks

[xnview]

Excuse Me , I have some problem about nconvert.
I Use The Command .
nconvert -ratio -resize 400 0 PICT0001.JPG
after resize the image ,I also use IrfanView(Picture software) to resize The same picture
the result is

source PICT0001.JPG File Size : 970KB
use nconvert resize PICT0001.JPG :File Size : 119KB
use IrfanView resize PICT0001.JPG : File Size : 30KB

so I don't Why come to the result ? Thanks

You can use -q for output quality

[helmut]

The JPG format is lossy and allows for saving with various quality levels. With -q you can set the quality level.

To get a better understanding of what the JPG quality level will mean to your image you could use the new export feature of XnView 1.90:
1.) Open an image in XnView
2.) Choose "File > Export..."
3.) As format choose JPG.
4.) Change the Quality parameters and press "Refresh" button to see result and new file size.

Following topics refer to XnView (and not nconvert) but give good background on aspects that influence file size:
- Smaller image has same file size
- Can you shrink a picture file size?
- Changing image sizes of scanned images
- Jpg compression after crop
- Data reduction on JPG images
- Resizing image results in larger file

Other related links
- How to prepare an image for the internet
- Common graphic formats
- What format should I save this image in?
- Lossy? Lossless? 256 colors? This is confusing!
- How to convert several images at once

[Guest]

THS A lot
It's my falut . I forgot use "-q"
thanks.