Search found 14 matches

by Dane Vandeputte
2014-02-05T12:21:41-07:00
Forum: Digital Image Processing
Topic: number of neighbors
Replies: 4
Views: 9382

Re: number of neighbors

If you're using the default interpolation, then you'll need to pad each slice of the original image with 2 pixels on each side. After a slice has been enlarged, you'll then need to crop off 2* scale pixels on each side. For example, if scale = 16, meaning that each dimension will become 16 times lar...
by Dane Vandeputte
2014-01-13T10:32:39-07:00
Forum: Digital Image Processing
Topic: 5 new interpolation kernels
Replies: 10
Views: 21195

Re: 5 new interpolation kernels

I still think that good things could be obtained through a judicious use of Binomial as a replacement for Gaussian. I think it is also interesting to consider the Kaiser window, extended to include its first zero on either side of the y-axis. As the alpha parameter is varied, the extended Kaiser wi...
by Dane Vandeputte
2013-01-02T19:50:12-07:00
Forum: Digital Image Processing
Topic: 5 new interpolation kernels
Replies: 10
Views: 21195

Binomial window... as I see it, anyways :)

The probability mass function of the binomial distribution is: binomial(n, x)*(1 - p)^(n - x)*p^x. In order that the distribution is not lop-sided, we use p = 1/2. This simplifies to: binomial(n, x)/2^n. Of interest is n >= 0 and 0 <= x <= n. Scaling and shifting the distribution so that x is mapped...
by Dane Vandeputte
2012-10-25T20:00:11-07:00
Forum: Digital Image Processing
Topic: Convert JPEG from progressive to baseline losslessly
Replies: 14
Views: 43764

Re: Convert JPEG from progressive to baseline losslessly

Nemo_bis wrote:Thank you very much.
You're most welcome. :)
by Dane Vandeputte
2012-10-25T13:35:02-07:00
Forum: Digital Image Processing
Topic: Convert JPEG from progressive to baseline losslessly
Replies: 14
Views: 43764

Re: Convert JPEG from progressive to baseline losslessly

It "works" as in it produces a non-interlaced image from an interlaced one (and three times faster than convert), but I'm not able to say if this has been lossless. I can assume it was? Yes, it has been lossless. The -perfect isn't necessary in this case, but it doesn't hurt. Also, if you want to k...
by Dane Vandeputte
2012-07-22T11:11:37-07:00
Forum: Users
Topic: Don't use linear light when enlarging with Lanczos et al
Replies: 27
Views: 30978

Re: Don't use linear light when enlarging with Lanczos et al

NicolasRobidoux wrote:
Dane Vandeputte wrote:...
Where is the nonlinearity?
Oops! Got my conversations crossed: I meant I'm curious to try XYZ with sigmoidalization (instead of linear RGB with sRGB primaries): viewtopic.php?f=22&t=21415.
Apologies.
No problem. :)
by Dane Vandeputte
2012-07-22T08:44:01-07:00
Forum: Users
Topic: Don't use linear light when enlarging with Lanczos et al
Replies: 27
Views: 30978

Re: Don't use linear light when enlarging with Lanczos et al

NicolasRobidoux wrote:
Dane Vandeputte wrote:...
Linear sRGB is related to XYZ through a simple matrix multiplication, so the results would be visually the same.
Nonlinearity beware! I don't expect a huge difference, but I expect one.
Where is the nonlinearity?
by Dane Vandeputte
2012-07-21T21:35:03-07:00
Forum: Users
Topic: Don't use linear light when enlarging with Lanczos et al
Replies: 27
Views: 30978

Re: Don't use linear light when enlarging with Lanczos et al

NicolasRobidoux wrote:Although I don't have time for this right now, this is why I'd be curious to compare enlarging through linear RGB with sRGB primaries with enlarging through XYZ.
Linear sRGB is related to XYZ through a simple matrix multiplication, so the results would be visually the same.
by Dane Vandeputte
2012-07-13T19:45:21-07:00
Forum: Users
Topic: Don't use linear light when enlarging with Lanczos et al
Replies: 27
Views: 30978

Re: Don't use linear light when enlarging with lanczos et al

I fully agree that enlarging via linear light is not a good idea, at least not without some sort of artifact reduction. Even then, I personally haven't seen enough perceptible advantage to bother. I think the reason behind this is that when upsampling, the interpolated values are generally not too d...
by Dane Vandeputte
2012-07-13T19:08:46-07:00
Forum: Users
Topic: best downsampling method for DSLR photographs
Replies: 273
Views: 383352

Re: best downsampling method for DSLR photographs

Dane: The Brasseur posting avoids filters with significant negative lobes, and only uses non-sharpening convolutions. I have not worked out the details yet so I'm not sure, but I believe that I may be able make the Dalai Lama disappear from the downsample through linear light without it disappearin...
by Dane Vandeputte
2012-07-02T16:10:29-07:00
Forum: Users
Topic: best downsampling method for DSLR photographs
Replies: 273
Views: 383352

Re: best downsampling method for DSLR photographs

Dane: I think that I assumed there was symmetry where there is not, and indeed the full size and reduced images are always most similar in linear light in this situation. Thank you! You're very welcome! (I really like how scrolling within my browser window makes the Dalai Lama jump up and down in t...
by Dane Vandeputte
2012-07-02T11:08:05-07:00
Forum: Users
Topic: How to rotate a *.jpg picture by 90 deg?
Replies: 4
Views: 71172

Re: How to rotate a *.jpg picture by 90 deg?

Even if the rotate 90 were lossless, just reading in a jpg and writing it out again would have some losses. JPG is a lossy compression image format. Actually, as it turns out, one can losslessly rotate by multiples of 90 degrees (or transpose) a JPEG file by doing nothing more than rearranging and/...
by Dane Vandeputte
2012-07-02T09:26:11-07:00
Forum: Users
Topic: best downsampling method for DSLR photographs
Replies: 273
Views: 383352

Re: best downsampling method for DSLR photographs

Thank you. I was glad to do it. :) But this is not quite what I meant. I meant: The Dalai Lama is visible in the full size image, disappears in the linear light toolchain image, and remains in the sRGB toolchain image. I believe that what you seek is impossible, at least by any method resembling wh...
by Dane Vandeputte
2012-07-01T19:29:40-07:00
Forum: Users
Topic: best downsampling method for DSLR photographs
Replies: 273
Views: 383352

Re: best downsampling method for DSLR photographs

I wager that Eric Brasseur, in his famous post http://www.4p8.com/eric.brasseur/gamma.html , could have fixed things so that the Dalai Lama disappears when downsized through linear light, but looks fine when processed through sRGB. Yes, this is possible, and just as the Dalai Lama disappears from t...