Reducing Image size without losing quality

[MN Lahmar]

Hello, i'm using PS and when i reduce an image (the image size, not file size) it loses its quality. How can i reduce it without losing quality?

 

[Vinz]

You can't. Unless everything is vector, which almost everything isn't. Unless you are using shapes, text, or the like, but they are so uncustomizable that it's impossible to make an image with them.

 

[PurgeandFire]

When you take a big image and shrink it down, it naturally will lose some detail (before the shrinkage, it had more pixels to display detail. After shrinking, it has fewer pixels, and as such, pixels need to be merged).

Photoshop allows you to resample an image after resizing it. This serves as a "smart" resizing method--photoshop will attempt to perform its own correction to the image to adjust it to the size. Resampling helps the most with sizing up (normally sizing up would cause pixellation, but resampling allows you to add new pixels. It may be blurry, but it is far better than a direct size-up)

Example of resampling when sizing up

Anyway, when you go to Image > Image Size, check "Resample Image". Experiment with the different options. Bicubic sharper is recommended for shrinking an image.

Also, it helps to keep the same proportions of the image. For example, 200x200 -> 100x100. When you change the proportions, you'll end up with stretching or compaction. Unfortunately, BLP's generally work with power of 2 dimensions, so preserving the original proportions isn't always an option.

 

[Chaosy]

Actually as long as you reduce the image size and not increase it, it shouldn't lose quality, no?

 

[PurgeandFire]

Actually as long as you reduce the image size and not increase it, it shouldn't lose quality, no?

You'll lose information from reducing image size (since it is mapping a large number of pixels down to a smaller range, so you lose particular details). It often doesn't look bad to our eyes though. But it is technically still a loss of quality, since detail is lost.

 

[Talavaj]

Actually nowadays due to the use of mesh gradients it is not impossible to create photorealistic vectors (you have probably seen them in marketing materials but never noticed) but the practical application of this is obviously very little.

Why would you want to make something smaller but retain its quality though ?
Generally you shouldn't notice the quality drop as the smaller picture will also take up less space on your screen and make it harder to notice anyway.

 

[GhostWolf]

If you end up converting to a BLP, you can to see if it has mipmaps, and delete them.
Mipmaps add ~33% of the memory.