upsampling of an image

[usman]

AOA!
how can i upsample an image. downsample is easy just not read the next pixel value. i tried read an image to m. and then tried m(1:0.5:end, 1:0.5:end) for upsampling but that didn't work, a warning "Warning: Integer operands are required for colon operator when used as index" is generated, so plz help me if any body knows something.

regards,

 

[manya]

I did not realy understand what u mean.If u want to unsample an already sampled signal,then i think this book can be of help.Otherwise explain your question again.

 

[itsthetimetodisco]

you will need to do interpolation to get the pixel values for upsampling.

 

[usman]

i mean i have an image 256x256. i want to upsample this image, how can i?

 

[itsthetimetodisco]

From 256x256, you can do pixel replication OR biliinear interpolation OR cubic interpolation to upsample your image. Here is a link I found which gives implementation code to upsample image using sinc function:
**broken link removed**
Hope this helps.

 

[mumtaj]

u can use the following code:

(eg):

im=imread('rice.tif');
x=upsample(im,f);

where f is the upsampling factor
u may choose ur own value for "f" (eg:2 or 3)