OT: Reducing an image's size in Photoshop without reducing quality

[teddyFBI]

I've been trying to create several deck and image mods in photoshop, but find that invariably whenever I try to reduce the actual size of an image, the quality goes to [censored] -- is there a trick i should know about that would prevent this from happening?

[TheTROLL]

You may find dividing the number of pixels in the dimensions by an exact integer helps (eg, scale to 50%, not 55%), though it depends on the content of the image to some extent.

When you say reduce the size, I presume you are talking about bytes and not dimensions. By the very nature of images, more detail requires more bytes. It also depends on what you're coming from. If you're reducing the size of a JPG, you should know that JPG uses lossy compression, meaning each time you open it up and save it again, you LOSE quality. If the dimensions are what you want, you're in a bind. You can reduce DPI as low as 72 (if it is going to be displayed on a computer screen - but not for printout). Other than that, save it as a JPG with the lowest quality setting that you think has an acceptable quality. That's about all you can do.

[teddyFBI]

[ QUOTE ]
When you say reduce the size, I presume you are talking about bytes and not dimensions. By the very nature of images, more detail requires more bytes. It also depends on what you're coming from. If you're reducing the size of a JPG, you should know that JPG uses lossy compression, meaning each time you open it up and save it again, you LOSE quality. If the dimensions are what you want, you're in a bind. You can reduce DPI as low as 72 (if it is going to be displayed on a computer screen - but not for printout). Other than that, save it as a JPG with the lowest quality setting that you think has an acceptable quality. That's about all you can do.

[/ QUOTE ]

I knew i phrased that question badly.
No, I'm talking about reducing the DIMENSIONS of a picture. For example, I'm trying to reduce the height of a card from 77 pixels to 70 pixels, and when I do that, the edges of the digits on the card get all fuzzy and somewhat distorted, even with that small a change. Any tips for reducing the dimensions of a picture without that happening?

[TheTROLL]

Not for that sort of scale change - think about what you're asking the software to do: imagine the image were 7x7 and you want it to be 6x6. You can't just chop out an arbitrary pixel, it might be crucial to the image... so you have to "average" out that pixel's colour across the surrounding pixels, turning fine lines into blurs. As posted earlier, halving dimensions works well, since you are combining pairs of pixels into a single pixel. Trying to remove 10% of the pixels is inherently problematic.

[StevieG]

The Troll speaks true

try cropping as much as possible before scaling down

[Mr Gee]

Working on images at such a small scale can be quite tricky. Resizing is rarely very satisfactory when every pixel counts. You could try using an icon editing package instead, where you work with a pixel based grid. Might take a little longer, but it would give you more accurate control. Something like IconCool.