Enlarging raster vs vector Objects

IA
Posted By
i_am_jim
Apr 16, 2008
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306
Replies
12
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Closed
as i understand it vector objects should enlarge without losses, while raster objects pixilate on enlargement.

In this image
http://img212.imageshack.us/img212/6178/triangleswithrasterc z0.gif the top triangle is raster. The bottom one is vector. Otherwise the two are identical. I stretched both about 15 fold using transform. They are identical. If you magnify them to 800 times actual size the pixilation is the same. So, the raster image enlarged exactly the same as the vector image??????
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JJ
John Joslin
Apr 16, 2008
When a vector object is rendered into a GIF or JPEG it becomes rasterised.

You can only retain vector information in a file format that supports it.
JM
John_Mensinger
Apr 16, 2008
Plus…don’t forget that the monitor screen you’re looking at…and the printer you’re printing to…render their result on a grid of pixels/dots as well.

The difference is that scaling a vector graphic re-renders the same mathematical formula at the new size, whereas scaling a raster requires pixel-based interpolation, which must either throw pixels away, (scaling down), or manufacture new pixels, (scaling up).
IA
i_am_jim
Apr 16, 2008
On Wed, 16 Apr 2008 05:15:26 -0700,
wrote:

Plus…don’t forget that the monitor screen you’re looking at…and the printer you’re printing to…render their result on a grid of pixels/dots as well.

The difference is that scaling a vector graphic re-renders the same mathematical formula at the new size, whereas scaling a raster requires pixel-based interpolation, which must either throw pixels away, (scaling down), or manufacture new pixels, (scaling up).

Somehow I’m not being clear. I understand the difference between vector and raster objects/images. My point is, theoretically upsizing a vector image should give a different (better/cleaner/smoother ) result than resizing a raster image. Yet, in my example upsampling by a factor of 15 times showed no difference.
CY
curt_young
Apr 16, 2008
Re-read message 1.
DM
Don_McCahill
Apr 17, 2008
Your sample image is a gif. A gif is a raster image, no matter whether it was created from vector elements or raster. You lose the vectors when the gif is created.

If you create that same image again within Photoshop, you will be able to upsample the image 15x and find the vector triangle remain sharp, which the raster one goes fuzzy. But if you convert to a different file format first, then this will not happen.

I hope that clarifies the information in message 1.
EG
Ed_Grenzig
Apr 18, 2008
I am Jim

In PSCS3 it works fine for me. I create 2 identical objects, one raster, one vector and in large by resampling both, (10x). I also in large by using the Transform scaling command. In both methods the vector remains smooth and the raster looks worse around the edges.

Ed
P
Phosphor
Apr 18, 2008
BUT!

If one uses the "Nearest Neighbor" resampling algorithm, it’s very possible that a GIF shape could look nearly identical to the enlarged vector object once the vector object is rendered as a raster image (which of course, it the only way Photoshop will display it).
IA
i_am_jim
Apr 19, 2008
On Thu, 17 Apr 2008 06:09:32 -0700,
wrote:

Your sample image is a gif. A gif is a raster image, no matter whether it was created from vector elements or raster. You lose the vectors when the gif is created.

If you create that same image again within Photoshop, you will be able to upsample the image 15x and find the vector triangle remain sharp, which the raster one goes fuzzy. But if you convert to a different file format first, then this will not happen.

I did the enlargement in Photoshop BEFORE making the image into a gif so I could show people the issue.
IA
i_am_jim
Apr 19, 2008
On Fri, 18 Apr 2008 03:38:38 -0700, wrote:

I also in large by using the Transform scaling command. In both methods the vector remains smooth and the raster looks worse around the edges.

That’s very strange. As you can see from the illustration I posted, after using the Transform scaling to enlarge the two triangles about 15 fold there is no apparent difference.

NOTE: I get the difference if I enlarge by resampling the entire image, but not when using Transform.
EG
Ed_Grenzig
Apr 19, 2008
I-am-Jim wrote

NOTE: I get the difference if I enlarge by resampling the entire image, but not when using Transform.

Jim
I tried again and again the vector image was much better. I created a vector circle using the shape tool. Duplicated the vector layer and then rasterized one layer. The canvas is 1000 x 1000 pixels and the circles created at 100 x 100 pixels (one vector, one rasterized layers). I used the edit/transform to enlarge each layer by about 10x. Stretched them about 10x using the transform handels. The vector image looks great, the rasterized layer is very jagged.

Ed
JH
John_Hunly
Apr 20, 2008
That is what is supposed to happen. Raster doesn’t enlarge well, vector can be enlarged to nearly any size quite well.

John
DM
Don_McCahill
Apr 20, 2008
I did the enlargement in Photoshop BEFORE making the image into a gif so I could show people the issue.

Ah, sorry for the confusion. The reason then is probably the one given by Phos in message 7.

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