Affinity Photo: Reduce superfluous data

[Pyanepsion]

Hello everyone,

I have an original JPEG image of 7479 × 11,146 pixels.

It should therefore have a theoretical storage capacity of 7,479 × 11,146 = 83,360,934 bytes (79.50 MB).

However, it is 89.9 MB (94,314,496 bytes). How can I remove the superfluous information?

Thank you for your explanations.

[Ron P.]

Affinity Photo Tutorial: Compression Efficiency

 

[Joachim_L]

11 minutes ago, Pyanepsion said:

How can I remove the superfluous information?

Exporting with no metadata or ICC profile could be an option.

[Pyanepsion]

Here is the link to the original image. I would like to delete only the added information to return to 83,360,934 bytes (79.50 MB).

The Mona Lisa

[Ron P.]

Is it that critical to have the 79.50MB file size?

• What and how was this superfluous information  added?
• Did you do any processing to the image that may have added to the file size?

Checking the file size in the Export dialog of AP, it shows it to be at 100% to 102.33MB, just changing the compression quality to 95% reduces the file size to 51.67MB. (See screenshots).

I also tried in XnView Convert. It also reduces it to less than what you're asking.

[walt.farrell]

1 hour ago, Pyanepsion said:

I have an original JPEG image of 7479 × 11,146 pixels.

It should therefore have a theoretical storage capacity of 7,479 × 11,146 = 83,360,934 bytes (79.50 MB).

Your image has 83,360,934 pixels, not bytes. Each pixel requires (for RGB/8) 24 bits, which gives you an uncompressed size of 2,000,662,416 bits.

So, uncompressed, it is 250,082,802 bytes, or 238.5 MB.

But as we know, the JPG format involves compressio, and getting it down to either 89.9 or 79.5 MB is largely a matter of how you perform that compression, which for JPG generally starts with the quality level you choose when Exporting the file. Beyond that it's a question of how well the compression algorithms perform, and you have no control over them in Affinity, but there are optimization programs that can reduce file size.

(And if you are using Affinity Photo, and started your session with a JPG image, you will certainly want to use File > Export rather than File > Save. Only Export gives you any control over the Quality setting.)

 

[Ron P.]

Geesh, too early to do math. Missed the pixels vs bytes completely. 🤔

[Pyanepsion]

Thank you, @walt.farrell.

Me too, @Ron P..

To conclude:

Original: 89,9 Mo (94 310 471 octets) in JPG.
- In JPG, 100%, without ICC profile and without metadata, this image measures 102 MB (107,304,429 bytes) 102 MB (107,304,429 bytes)
- In PNG, the image is 157 MB (165,194,655 bytes)
- In TGA, the image measures 238 MB (250 082 846 bytes)