image-processing

How to use DoG Pyramid in SIFT

Hi all, I am very new in image processing and pattern recognition. I am trying to implement SIFT algorithm where I am able to create the DoG pyramid and identify the local maximum or minimum in each octave. What I don't understand is that how to use these local max/min in each octave. How do I combine these points? My question may sound...

Object Recognition from Templates

Hi Guys, I was hoping someone could point me in the right direction here. With a picture of a die (from above) I want to recognize which side is up. I understand the basics in play here, but I'm having trouble grasping the power of OpenCV. I imagine I want a picture of each side of the die. Then I can somehow compare them all to the...

Finding many local max in an image (using MatLab)

How do you go about figuring our multiple max in a 2D image where the max aren't necessarily all the same height? I have found that the imregionalmax(), imextendedmax(), and findpeaks() functions aren't necessarily that helpful because they give many local max that are really just maxes within the background noise. I tried bw=array>imdi...

How do I count the number of persons in an image using MATLAB?

Has anyone ever tried doing this kinda job? ...

User avatar cropping/resizing with paperclip and jquery in rails

Hello fellow stackoverflow users. I am building my first Ruby on Rails app which is going to be my own little community. I have made the User model with several fields and information. But now i am thinking of adding avatar support for the users. And i've been researching and found that my best option would be using Paperclip. But then ...

Finding a small image in a bigger one

Possible Duplicate: Matching a rotated bitmap to a collage image Given an image with a large dimension (> 1.000 x 1.000). What is a good approach to find a small image (e.g. 50 x 50) in the big one? The smaller image can be rotated and differ in the size, but only with a 1:1 ratio. It's not related to any programming langua...

How to get path of stroke using opencv ?

I want to get path stroke from image using opencv. I know how to get contours but I need path of stroke (path that runs through the center of the stroke). Is it possible to get this in opencv ? ...

Most optimal way to detect if black (or any color pixels) exist in an image file?

What's the best and most flexible algorithm to detect any black (or colored pixel) in a given image file? Say I'm given an image file that could, say, have a blue background. And any non blue pixel, including a white pixel, is counted as a "mark". The function returns true if there are X number of pixels that deviate from each other at ...

Determine illuminance from RGB image

Is there a way to use camera (web camera or phone camera) as a light meter? Phone camera can grab image and get data in RGB format, but has anyone tried to determine illuminance value (in lux)? I am aware that there is no formula to do this (correct me if I am wrong), but is it possible to model it, and get an approximate value of illum...

Standardize color within an image

I have a .net application where I need to browse for an image, I would like to standardize the colors in the image to just 6 colors? Is there a library or process to perform this kind of image manipulation? Any help would be appreciated... Thanks, Mike ...

How do I apply a median filter to a UIImage on the iPhone?

I would like to improve my OCR accuracy (I'm using the Tesseract OCR engine) by using a median filter on an image before performing OCR on it. How would I apply a median filter to a UIImage instance? Thanks! ...

Java: Detect if image isGIF or isTIFF and convert to JPG

I have a Java website, now Ive build an uploader, the validation for JPG images is done and a way to save it into the server it is too. But now I need to create an utility class using isGIF and isTIFF validated them by byte[] and convert that byte[] to java.awt.Image to save as JPG So basically I need boolean isGIF(byte[]), boolean isT...

How to read pixel values of a video?

I recently wrote C programs for image processing of BMP images, I had to read the pixel values and process them, it was very simple I followed the BMP header contents and I could get most of the information of the BMP image. Now the challenge is to process videos (Frame by Frame), how can I do it? How will I be able to read the headers ...

Paperclip Resize to fit a rectangular box

I have a rectangular image for example 30x800 pixels How I can scale it with paperclip to preserve the aspect ratio to a 100x100 pixel image with borders filling the empty area ? an example : http://www.imagemagick.org/Usage/thumbnails/pad_extent.gif ...

Standardizing camera input in OpenCV? (Contrast/Saturation/Brightness etc..)

I am building an application using OpenCV that uses the webcam and runs some vision algorithms. I would like to make this application available on the internet after I am done, but I am concerned about the vast differences in camera settings on every computer, and I am worried that the algorithm may break if the settings are too differen...

Using MatLab to calculate signal:noise ratio

How do you use MatLab to calculate the SNR? Update I only have one file, not two like in the example and it's a .tif. ...

Convert large raster graphics image(bitmap, PNG, JPEG, etc) to non-vector postscript

How to convert an large image and embed it into postscript? I used to convert the bitmap into HEX codes and render with colorimage. It works for small icons but I hit a /limitcheck error in ghostscript when I try to embed little larger images. It seem there is a memory limit for bitmap in ghostscript. I am looking a solution which can ...

How would I write the following applescript in Obj-C AppScript? ASTranslate was of no help =(

The translation tool isn't able to translate this working code. I copied it out of a working script. set pathToTemp to (POSIX path of ((path to desktop) as string)) -- change jpg to pict tell application "Image Events" try launch set albumArt to open file (pathToTemp & "albumart.jpg") save albumArt...

Simple C image library?

What's the simplest C image library for loading and saving? I just want a 2D array to test some algorithms, and built-in functions are not needed. ...

Reducing moire when downsampling halftone comic images.

How can I reduce moire effects when downsampling halftone comic book images during live zoom on an iPhone or iPad? I am writing a comic book viewer. It would be nice to provide higher resolution images and allow the user to zoom in while reading the comic book. However, my client is averse to moire effects and will not allow this feat...