Why can't Photoshop shrink a pic but Windows Picture Viewer can?

[Brent212]

I've encountered this same phenomenon on several occasions so I figured I'd ask if anyone can explain it to me.

I'll open a gif that's bigger than I'd like in Photoshop 6.0, go to "Image"-->"image size" (I think that's it... don't have photoshop on my current machine), and enter a number in pixels smaller than it's current size. I keep the proportions constrained. After the operation is complete the picture looks like crap. The text especially is difficult to read and lines are "jaggy". There are three options in the resizing window -- bicubic, nearest neighbor, and something else... I think it's bilinear. I've tried them all and couldn't notice a difference.

I've done the same thing in another picture viewer/editor that I like to use, Polyview. Same result. Picture looks like crap.

In both programs I've also tried saving the pic as a 24-bit bmp, closing it, and opening the bmp version to do the resizing on. No difference (that I could see).

I can see Polyview, which is sharware, doing a less than perfect job, but you'd think an expensive program like Photoshop could do this as good, if not better, than any other program.

Now for the thing that really gets me. If I just open the gif up in Windows Picture Viewer (right clicking the file and selecting "Preview" will do this), I can resize the window, which resizes the picture (or "preview"), and get it to be any size I want, and it always looks good... better than good, it looks F-ing perfect. The text is crisp and clear, and nothing is distorted.

Why is it that a simple viewer that comes with Windows can do this (though unfortunately it can't save the resized pic), but a high-end piece of software like Photoshop can't? Seems a little ridiculous, and makes me think that I just don't know the proper way to do it in Photoshop.

Comments/enlightenment welcome.

[thecoalman]

Upload some samples of the before and after.

One thing to be aware about gif's is that the save options after you resize can have varying affects on how it looks and the file size. Gif is only 256 color and settings like ditthering can make a world of difference for some pics.

[Brent212]

Removed... will try again in a sec

[Paul_G]

Total user error and what's worse is you have made quite a few misleading and totally untrue comments about photoshop.

Why can't Photoshop shrink a pic but Windows Picture Viewer can?

Windows picture viewer can not and does not shrink/resize anything at all, just look on the creators site. As for Polyview, did you actually read what that does? because your spreading misinformation about that program also.

and makes me think that I just don't know the proper way to do it in Photoshop.

Exactly.

[Brent212]

I'm not sure that gifs are always only 256 colors. Regardless, it's irrelevant since the colors on the resized pics are fine, and even if they weren't, I'm focused on the way the pic gets distorted when shrunk.

Here is an example:

Original pic:


Resized pic:


Resized in Windows Preview, pasted into Photoshop by doing a "print screen":


Maybe I should just do the print screen method... seems to work pretty well actually. Just a little cropping needed.

The difference is especially noticeable on the text and on the diagonal line on the teepee and picnic table.

[Brent212]

Total user error and what's worse is you have made quite a few misleading and totally untrue comments about photoshop.

Why can't Photoshop shrink a pic but Windows Picture Viewer can?

Windows picture viewer can not and does not shrink/resize anything at all, just look on the creators site. As for Polyview, did you actually read what that does? because your spreading misinformation about that program also.

and makes me think that I just don't know the proper way to do it in Photoshop.

Exactly.

Thanks for all the help. You might be correct if I hadn't admitted in my post that I very well could be missing something. I never claimed that either program could definitely not do a good job resizing. How about instead of being a dick, you describe what to do to get the results I'm after?

[jagabo]

I don't use Photoshop but this is universal: before resizing convert the image to 24 bit color. Then resize with a Bicubic filter.

[Brent212]

I don't use Photoshop but: before resizing convert the image to 24 bit color. Then resize with a Bicubic filter.

Thanks for the suggestion. I have done that, but apparently I'm not resizing it correctly (I'm guessing that's what paul meant in his informative response above).

[thecoalman]

I'm not sure that gifs are always only 256 colors.

They are always 256 colors or less, and how you use them can have varying affects. Just as an example the image you posted from the windows preview, you're adding colors to that and if the original had many different colors you would have had to "rob peter to pay paul" to compensate for the new colors. The 256 colors is probably the root of of your problem. I don't have Photoshop either but Ulead Photoimpact, I get similar results to yours when resizing the GIF, the text is little better but not much.

Anyhow converting it to true color, then saving as GIF, no dithering using a detailed color palette gives pretty decent results but this also produces a very large file at these settings:

[jagabo]

Typicially, when resizing a palettized image the resizer will use a nearest neighbor algorithm -- because there may be no in-between colors which might be generated by a more advanced filter. If you convert to 24 or 32 bit truecolor the resizer usually gives you various filtering options like Bilinear, Bicubic, Lanczos.

[ahhaa]

some programs have both resize & resample options; and if you don't save the file after going to true color, they may use just the 256... this happens with older versions of Paint Shop Pro for ex.

another trick to keep fonts clear is to increase the size while doing the conversion to 24 bit, use Sharpen, Median, etc as needed, then reduce to needed size.

You could also use the magic eraser to delete the text from the gif then reinsert after the resizing...

[Brent212]

I've tried with no luck:
1) saving the gif as 24-bit bitmap.
2) opening bitmap
3) resizing
4) saving as a 24-bit bitmap

Resulting pic looked the same as if I left it as a gif the whole time. I don't have any desire to keep it as a gif, that's just the format the original happened to be in in this case. I've had this same issue with jpeg originals before.

That being said, I was able to figure out what was causing the shitty resizing in both Photoshop and Polyview.

In Photoshop, I went to Image-->Mode and switched it from "Indexed Color" to "RGB Color". I've never messed around in the "Mode" menu, so I'm not sure if it just defaults to "Indexed Color" or if I somehow accidentally set it to that, but regardless, now resizing even the original gif works great.

In Polyview, a newer version I have on one computer has an option to select which type of resampling method to use. It was set to nearest neighbor. I switched it to bicubic and it looked great. I never noticed this option, probably because an older version I have on another computer doesn't have it, though I just tried resizing on there and it looks good also, so it must use bicubic also, or at least something better than nearest neighbor. I did try reading about what Polyview does, as paul suggested, but I couldn't find the part about switching the resampling method on the newer version from nearest neighbor to bicubic to improve the quality of a shrunken image. Maybe because that's not really specific to just that application...

So both cases were operator error, like I was suspecting. Stoked to have it figured out. Thanks for the replies.

[jagabo]

In Photoshop, I went to Image-->Mode and switched it from "Indexed Color" to "RGB Color". I've never messed around in the "Mode" menu, so I'm not sure if it just defaults to "Indexed Color" or if I somehow accidentally set it to that, but regardless, now resizing even the original gif works great.

All the programs I've used automatically switch from indexed (palettized) color to RGB (truecolor) when you change the image's color depth.

In case you don't know: indexed color is a paint-by-numbers scheme. When you paint a pixel in indexed mode you put a single number in it. That number is an index into a lookup table of RGB values. To show that pixel on the screen a the index number is converted to an RGB value (via the lookup table) for display.

In truecolor modes the actual values stored in the pixel are the RGB values.

[DarrellS]

In Photoshop, I went to Image-->Mode and switched it from "Indexed Color" to "RGB Color". I've never messed around in the "Mode" menu, so I'm not sure if it just defaults to "Indexed Color" or if I somehow accidentally set it to that, but regardless, now resizing even the original gif works great.

I've had that problem before where the color mode got switched. I believe but I could be wrong that RGB is default mode (it's what I always work in anyway). I usually check to make sure when I'm working with Photoshop since sometimes images open up in a different mode if you're working with Gif or grayscale images.

[thecoalman]

Typicially, when resizing a palettized image the resizer will use a nearest neighbor algorithm -- .

In Photoimpact you have the choice of the three when working with GIF, however it produces the same results, or it appears to. I didn't examine it closely. I'm guessing it's a"fake" selection.

[jagabo]

Typicially, when resizing a palettized image the resizer will use a nearest neighbor algorithm -- .

In Photoimpact you have the choice of the three when working with GIF, however it produces the same results, or it appears to. I didn't examine it closely. I'm guessing it's a"fake" selection.

Yes, I use PhotoImpact too. It always does nearest neighbor in indexed 256 color mode, even though the filter pulldown is still enabled.

[lordsmurf]

GIFs use indexed color. Photoshop respects this.

When you resize an image, anti-alias filters kick in. This means more colors can be created to give the illusion of a perfect resize. When you constrain your color palette, it cannot make the new colors, so your image looks like crap.

Goto IMAGE -> MODE -> and change it to RGB palette.

Resize your image.

When you SAVE FOR WEB to create the new GIF, it will re-index the colors in the image. The number of colors depends on your compression. For web-compliant imaging, you need to pick 32-bit minimum, 128-bit maximum. Dithering is optional, and can sometimes make an image look better, if the image palette was larger than the index being allowed. It is one way you can fight posterization.

This was a keyboard-chair interface error. But it's not an obvious process, so you're completely excused. Just remember you're using professional software here, not all-in-one idiotware.

Good luck with your image/photo work.

[thecoalman]

Dithering is optional, and can sometimes make an image look better, if the image palette was larger than the index being allowed. It is one way you can fight posterization.

I find dithering very beneficial for "real" images, or if you have gradients. Skies seem to be the worst offenders and you will inevitably get posterization without dithering. I don't use it much though because 99% of the gifs I'm creating are either icons or small images.

[Brent212]

I was able to figure out what was causing the shitty resizing in both Photoshop and Polyview.

In Photoshop, I went to Image-->Mode and switched it from "Indexed Color" to "RGB Color". I've never messed around in the "Mode" menu, so I'm not sure if it just defaults to "Indexed Color" or if I somehow accidentally set it to that, but regardless, now resizing even the original gif works great.

Goto IMAGE -> MODE -> and change it to RGB palette.

This was a keyboard-chair interface error.

Well, at least I figured it out after awhile, so I'm not a complete tard.