Filesize doubles with batch-editing

[infosauger]

When I open a picture (jpg) with a rotation Info and just safe it (lossless settings) the filesize just changes to slightly smaller (Example: Original 4MB -> 3,62MB).
When I rotate the same picture in one direction and back, the size changes to 3,86MB.
When I start a batch job and set the editing to rotate to EXIF-Direction with the same settings for jpg (lossless) the filesize changes from 4MB to 10MB.
I tried to find a pixel difference with GIMP between the Original and the new file but didn’t find anything. What uses this extra space?

[xnview]

Do you means batch lossless transformations or batch convert?

[infosauger]

right click on picture -> batch convert -> action: rotate (EXIF Orientation) -> output: Format (same as original); settings (JPEG: 100%; JPEG-XR: 100%; JPEG-XL: lossless compression)

Original picture: JPEG TrueColor (c1.1)

[xnview]

your original picture is perhaps not compressed at 100%

[infosauger]

your original picture is perhaps not compressed at 100%

Hm, if the original picture isn't compressed at 100% but the target one is, shouldn't then the target file be much smaller instead of much larger?

[xnview]

if you original file is compressed for example to 70, if you compress it at 100% you'll have a higher file size

[infosauger]

Do you means batch lossless transformations or batch convert?

Lossless transformation is the only rotation option, that is not lossless. It cuts Pixels on the border.
The other 3 rotation options (1: Save picture in picture window; 2: Batch transformation with rotation action; 3: export to JPG) result in 100% ident images (checked with GIMP) but complete different filesizes: Original File: 3,79MB; Option 1: 3,16MB; Option 2: 9,45MB; Option 3: 6,52MB.

[xnview]

"batch convert -> action: rotate (EXIF Orientation)" is not lossless, only "JPEG lossless transformations"

[infosauger]

"batch convert -> action: rotate (EXIF Orientation)" is not lossless, only "JPEG lossless transformations"

Sorry, but that's wrong.

I tried JPEG lossless transformations and width changed from 2988 pixels to 2984 pixels. The remaining picture is 1:1 with the original
I also tried "batch convert -> action rotate (EXIF Orientation) with 100% quality and the picture is 1:1 with original.

I opened both files and the original with GIMP and there is no pixel-difference except the 4 pixels on the right side after "JPEG losless transformation".

Maybe there is a setting for "JPEG lossless transformation" that it doesn't cut the picture, but I didn't find it.

[xnview]

I tried JPEG lossless transformations and width changed from 2988 pixels to 2984 pixels. The remaining picture is 1:1 with the original

Lossless rotation need that width is a multiple of 8, Batch convert re-compress image data

[infosauger]

Lossless rotation need that width is a multiple of 8, Batch convert re-compress image data

I understand, but why doesn't re-compress need a multiple of 8? Batch convert a landscape image with EXIF rotation info results in a 100% pixel-ident and 100% resolution-ident portrait image without EXIF rotation info.
Lossless rotation can result in loss of pixels, though the remaining pixels are 100% ident with the original. in my opinion calling it lossless when data is lost is just wrong.
Opening a landscape picture with EXIF rotation info is correctly shown as portrait. Just saving this picture results in a portrait image without EXIF rotation info and without loss of pixels it is 100% pixel ident with the original. It would be better if Lossless rotation would work exactly like this.

[xnview]

it's the way that lossless rotation works, encoded datas are not changed.
You can make lossless rotation by changing only the EXIF field

[infosauger]

it's the way that lossless rotation works, encoded datas are not changed.
You can make lossless rotation by changing only the EXIF field

Why doesn't batch rotation or lossless rotation work like "open picture->save picture"? As I mentioned, this way is really lossless, it doesn't cut pixels and the image is 100% ident with the original? And the filesize is simalar to the original one. But it takes time for many pictures.
All other ways generate 100% ident image, but need much more space.

[xnview]

batch convert & Save are not lossless, image datas are recompressed, but if you use 100% quality, there is no big loss

[infosauger]

batch convert & Save are not lossless, image datas are recompressed, but if you use 100% quality, there is no big loss

Wrong. I checked the Original picture with each version of the target picture with GIMP and THERE ARE NO PIXEL DIFFERENCES.
So they images are completley the same.