image-manipulation | 易学教程

training SIFT features in OpenCV

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问题 I have created a small SIFT application that grabs the keypoints and saves it out to a text file. I am using this to grab information from a logo (say AT&T) and use that to compare against other images with that logo. The problem is many of my images have variations of the logo that, due to the scaling, rotation, or lighting it does not pick it up. I was wondering if it was possible to get a set of images, grab it's keypoints, and run it through some sort of training algorithm to enhance the

Better image coloring logic/algorithm

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问题 I am developing an iOS app in which the user can change a part of an image's color, say a Tea Cup, by touching it. I am using Floodfill algorithm to fill colors so that the user has to tap on the Tea Cup to change its color. That's working fine. But, the final color looks little different than the replacement color. I have some problem finding out a better logic to convert the object's(Tea Cup) color to the selected color considering its saturation & lightness. I am using the following logic

image decoding and manipulation using JNI on android

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问题 background On some apps, it is important to handle large images without OOM and also quickly. For this, JNI (or renderscript, which sadly lacks on documentation) can be a nice solution. In the past, i've succeeded using JNI for rotating huge bitmaps while avoiding OOM (link here , here and here). it was a nice (yet annoyingly hard) experience, but in the end it worked. the problem the android framework has plenty of functions to handle bitmaps, but i have no idea what is the situation on the

C#/WPF image transformation over a trapezoid

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I have an image which I want to scale/stretch it over a trapezoid in WPF. Is there an easy way of doing it? I want to achieve 3D effect / perspective / bending. Basically taking a 2D image and bending it in 3D space. This is what I want to accomplish: original: new: * * * * * * * * Another note, I need this to happen very fast. I tried using this code, and the performance is unusable: http://www.vcskicks.com/image-distortion.php Any help would be greatly appreciated. Thanks a lot in advance! I think the easiest way to do this fast is using the WPF 3D . Just set-up a viewport with perspective

Remove white background from an image

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问题 I want to get a transparent background or no background for my images. I tried the '-background none' option and also the 'transparent' option, but the background image remains white. How can I achieve this? Please suggest. 回答1: If you are using Imagemagik then the command is: convert input.gif -transparent white output.gif However it will only work with a pure white background and not a shade of white. There are alternative and easier ways to do this with IrfanView or The Gimp or Photoshop

JS/jQuery Image Editor

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问题 has anyone stumbled upon image editor done either in pure JS, or jQuery - that kind like CKEditor has? I'm looking for piece of code, that adds handles to image, so you can resize it, or even drag image around, as you wish. Thank you. Edit: rephrased . 回答1: Here is wonderful image crop/resize JQuery plugin http://www.cropzoom.com.ar/ 回答2: Yes there are numerous online. Find here. jCrop is exceptional and awesome. 回答3: The way editors such as tinyMCE and CKEditor do it is like this <div

How to save a GIF on the iPhone?

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how can I save a GIF on the iPhone? The SDK includes only UIImageJPEGRepresentation and UIImagePNGRepresentation but nothing for GIFs or other image formats, is there a way to convert a UIImage to a GIF and save it? GM This is a library I wrote for encoding GIF images on the iPhone, if anyone reading this is interested: http://jitsik.com/wordpress/?p=208 You can't without a third party GIF library. The question is why do you need it to be GIF? PNG provides all that you might need and it is well supported. If you are trying to do animation, look at UIImageView's -animationImages property . 来源：

How to replace color of an image?

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问题 I want to replace color of an image. For example turn all blue colors to red without any distortion on shape. When i try this i can swap the colors by iterating every pixel, however the shape of the swapped area turns into a flat shape. example1 input : http://www.tutorialwiz.com/tutorials/changing_color/images/original.jpg example1 output: http://www.tutorialwiz.com/tutorials/changing_color/images/3.jpg example2: input output together : http://www.digital-photography-school.com/wp-content

java image crop

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I am aware of BufferedImage.getSubimage However, it cant deal with cropping images that are smaller than the cropping size throwing the exception: java.awt.image.RasterFormatException: (y + height) is outside raster I want to be able to crop either a PNG/JPG/GIF to a certain size however if the image is smaller than the cropping area centre itself on a white background. Is there a call to do this? Or do I need to create an image manually to centre the image on if so, how would I go about this? Thanks You cannot crop an image larger, only smaller. So, you start with the goal dimension,let's say

How to add extra meta data to PNG?

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is there a way to add some extra metadata to a PNG file and then retrieve it with PHP ? like Comment field. If you have ImageMagick installed, it comes with two utilities: mogrify and identify. To add comments: $ mogrify.exe -comment "My test comment" plogo.png To retrieve comments: $ identify.exe -verbose plogo.png | grep -i "comment:" comment: My test comment I don't know if mogrify/identify functions are available as PHP libraries, but you can always use the php system command. 来源： https://stackoverflow.com/questions/4497206/how-to-add-extra-meta-data-to-png