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Questions tagged [image-processing]

Anything related to digital image processing, i.e. the theory and the techniques used to extract or manipulate information from digital images.

Image Processing involves any kind of signal processing in which the input is an image. The output can also be an image, or it can be information relative to the input image. Most image processing techniques involve treating the image as a two-dimensional array and applying standard signal processing techniques to it. Though optical and analog image processing are both well defined in the space of image processing, the tag image-processing in SO solely refers to digital image processing.

A good start on the field is having a look at the next links:

For an in-depth collection of explanations of a number of image processing topics, have a look at CVonline.

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How to check if a specific pixel of an image is transparent?

Is there any way to check if a selected (x,y) point of a PNG image is transparent?
Danny Fox
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High Quality Image Scaling Library

I want to scale an image in C# with quality level as good as Photoshop does. Is there any C# image processing library available to do this thing?
Ramesh Soni
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Resize image proportionally with MaxHeight and MaxWidth constraints

Using System.Drawing.Image. If an image width or height exceed the maximum, it need to be resized proportionally . After resized it need to make sure that neither width or height still exceed the limit. The Width and Height will be resized until it…
Sarawut Positwinyu
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Show an image preview before upload

In my HTML form I have input filed with type file for example : Then I'm selecting multiple files by clicking that input button. Now I want to show preview of selected images before submitting form . How to do that…
Hardik Sondagar
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Resize image in PHP

I want to write some PHP code that automatically resizes any image uploaded via a form to 147x147px, but I have no idea how to go about it (I'm a relative PHP novice). So far, I've got images uploading successfully, filetypes being recognized and…
Alex Ryans
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Which library should I use for server-side image manipulation on Node.JS?

I found a quite large list of available libraries on Node.JS wiki but I'm not sure which of those are more mature and provide better performance. Basically I want to do the following: load some images to a server from external sources put them onto…
Andrei Андрей Листочкин
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How to sort my paws?

In my previous question I got an excellent answer that helped me detect where a paw hit a pressure plate, but now I'm struggling to link these results to their corresponding paws: I manually annotated the paws (RF=right front, RH= right hind,…
Ivo Flipse
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Image to ASCII art conversion

Prologue This subject pops up here on Stack Overflow from time to time, but it is removed usually because of being a poorly written question. I saw many such questions and then silence from the OP (usual low rep) when additional information is…
Spektre
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OpenCV & Python - Image too big to display

I have an image that is 6400 × 3200, while my screen is 1280 x 800. Therefore, the image needs to be resized for display only. I am using Python and OpenCV 2.4.9. According to OpenCV Documentation, If you need to show an image that is bigger than…
Zynk
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What Haskell representation is recommended for 2D, unboxed pixel arrays with millions of pixels?

I want to tackle some image-processing problems in Haskell. I'm working with both bitonal (bitmap) and color images with millions of pixels. I have a number of questions: On what basis should I choose between Vector.Unboxed and UArray? They are…
Norman Ramsey
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Image Segmentation using Mean Shift explained

Could anyone please help me understand how Mean Shift segmentation actually works? Here is a 8x8 matrix that I just made up 103 103 103 103 103 103 106 104 103 147 147 153 147 156 153 104 107 153 153 153 153 153 153…
Sharpie
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How do you composite an image onto another image with PIL in Python?

I need to take an image and place it onto a new, generated white background in order for it to be converted into a downloadable desktop wallpaper. So the process would go: Generate new, all white image with 1440x900 dimensions Place existing image…
Sebastian
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Algorithm to detect corners of paper sheet in photo

What is the best way to detect the corners of an invoice/receipt/sheet-of-paper in a photo? This is to be used for subsequent perspective correction, before OCR. My current approach has been: RGB > Gray > Canny Edge Detection with thresholding >…
Nathan Keller
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How does one convert a grayscale image to RGB in OpenCV (Python)?

I'm learning image processing using OpenCV for a realtime application. I did some thresholding on an image and want to label the contours in green, but they aren't showing up in green because my image is in black and white. Early in the program I…
user391339
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inverting image in Python with OpenCV

I want to load a color image, convert it to grayscale, and then invert the data in the file. What I need: to iterate over the array in OpenCV and change every single value with this formula (it might be wrong but it seems reasonable for me):…
Mansueli
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