Prev: Testing Neural network matlab code
Next: unreadable axis labels using latex interpreter when copying figures to powerpoint
From: Jose L. on 4 Jun 2010 17:20
ImageAnalyst <imageanalyst(a)mailinator.com> wrote in message <4bdbf067-5b40-4940-beaa-708a9e6ba39a(a)c13g2000vbr.googlegroups.com>...
> You could also write it to a temporary disk file, then use fread() to
> read it back in byte by byte into an array, so that you have all the
> header bytes along with the image data. Of course that won't work if
> you're not allowed to write anything to the hard drive. Why aren't
> you allowed to read from or write to the hard drive? Is it some kind
> of security thing? And if you can't write anything to the hard drive
> then why do you want the exact disk format of the image file? What
> would you do with it? If all you can do is display data but not read
> it or write/save it, then using just the image array alone would be
> sufficient - you shouldn't need all the format-specific stuff.

Hi ImageAnalyst,

Thanks for your answer. My question is only with the objective of know if the imwrite function have a performance similar with respect to other Matlab image procesing functions, i.e. imresize, imrotate, among others.

These functions (imrotate, imresize) do not needed write and read (imwrite/imread) the image, because that these it can asign directly in a variable (J = imresize(I,[100 100]);)

Thanks to all for your answers.
From: Walter Roberson on 4 Jun 2010 17:31
Jose L. wrote:

> Thanks for your answer. My question is only with the objective of know
> if the imwrite function have a performance similar with respect to other
> Matlab image procesing functions, i.e. imresize, imrotate, among others.

> These functions (imrotate, imresize) do not needed write and read
> (imwrite/imread) the image, because that these it can asign directly in
> a variable (J = imresize(I,[100 100]);)

imwrite() will definitely be slower, even for images too large to fit into the
primary cache (the fastest mass storage.)

The rule of thumb is that accessing the secondary cache is about 10 times
slower than accessing primary cache, and that accessing disk is about 10 times
slower than accessing secondary cache, for a net of disk accesses being about
100 times slower than primary cache.

You could reduce the writing speed by using a "RAM Disk", or a solid state
disk with an appropriate high-speed (e.g., SATA3) interface, but you will find
is that you are measuring the performance of the I/O subsystem rather than the
JPEG performance.
First  |  Prev  | 
Pages: 1 2
Prev: Testing Neural network matlab code
Next: unreadable axis labels using latex interpreter when copying figures to powerpoint