I am working on aerial RGB image classification. Can any expert kindly comment which descriptor would be better for fair classification? Gabor descriptors or SIFT descriptors?
Thanks much in advance
Actually, both features are OK, you can try both of them.
SIFT is usually used in normal image and aerial image, however, Gabor descriptor is more often applied to aerial image.
Check this paper[1] for more information.
[1]: Comparing SIFT descriptors and Gabor texture features for classification of remote sensed imagery, ICIP 2008
Related
I have a sequence of images taken from a camera. The images consists of hand and surroundings. I need to remove everything except the hand.
I am new to Image processing. Would anyone help me in regard with the above Question. I am comfortable using C and Matlab.
A really simple approach if you have a stationary background and a moving hand (and quite a few images!) is simply to take the average of the set of images away from each image. If nothing else, it's a gentle introduction to Matlab.
The name of the problem you are trying to solve is "Image Segmentation". The Wikipedia page here: wiki is a good start.
If lighting consistency isn't a problem for you, I'd suggest starting with simple RGB thresholding and see how far that gets you before trying anything more complicated.
Have a look at OpenCV, a FOSS library for computer vision applications. Specifically, see the Video Surveillance module. For a walk through of background subtraction in MATLAB, see this EETimes article.
Can you specify what kind of images you have. Is the background moving or static? For a static background it is a bit straightforward. You simply need to subtract the incoming image from the background image. You can use some morphological operations to make it look better. They all depend on the quality of images that you have. If you have moving background I would suggest you go for color based segmentation. Convert the image to YCbCr then threshold appropriately. I know there are some papers available on it(However I dont have time to locate them). I suggest reading them first. Here is one link which might help you. Read the skin segmentation part.
http://www.stanford.edu/class/ee368/Project_03/Project/reports/ee368group08.pdf
background subtraction is simple to implement (estimate background as average of all frames, then subtract each frame from background and threshold resulting absolute difference) but unfortunately only works well if 1. camera has manual gain and exposure 2. lighting conditions do not change 3.background is stationary. 4. the background is visible for much longer than the foreground.
given your description i assume these are not the case - so what you can use - as already pointed out - is colour as a means of segmenting foreground from background. as it's a hand you are trying to isolate best bet is to learn the hand colour. opencv provides some means of doing this. if you want to do this yourself you just get the colour of some of the hand pixels (you would need to specify this manually for at least one frame) and convert them to HUE (which encapsulates the colour in a brightness independen way. skin colour has a very constant hue) and then make a HUE histogram. compare this to the rest of the pixels and then decided if the hue is simmilar enough.
I'm working on a web application that will allow users to upload profile pictures (avatars, basically). These images will be no bigger than 100 x 100 pixels and will be pictures of peoples' faces.
We want to allow the user to upload various image formats, but we also want to convert them all to the same image format. What would be the best image format for size, quality, etc.?
Edit
In this case, size is more important than quality, but not by much.
For faces, JPEG is your best bet. Even a relatively high quality JPEG image will be significantly compressed relative to the alternatives.
The JPEG format (and the way its compression works) was designed for "natural" images like photographs. (The alternatives, primarily GIF and PNG, work better for computer graphics, diagrams, etc.)
All that said, you should try it. Take a couple of example photos, convert them to the various image formats, and see how they compare (with apologies for the subject matter! 8-)
JPEG, 6,668 bytes:
(source: entrian.com)
PNG, 31,651 bytes:
(source: entrian.com)
I think JPG is best for avatars, I cant find a need for transparency.
JPG will be ok for photographs and will be overdo for graphics, but it's not a huge size overhead for 100x100
With an image of such limited size, and considering the profile pictures will most likely be a natural image JPEG is most certainly the way to go.
PNG works great when handed a very repetitive pattern. Computer generated graphics like screenshots, gradients. There are a couple of filters that increase the effectiveness of the deflate, however due to the losless nature of PNG, you will almost never get similar compression ratio's on these kinds of images.
If i have a logo, let's say done as a jpg or even a png. Any suggestion for how I can use that to define a path geometry? It would be really good if any suggestions could be provided for how i can do it in blend.
Thanks
Yes - I just tackled this problem for an LOB application two days ago.
I can't offer advice for Blend (though I've read that it can be done in Expression Designer). However, the best free tool I've found for this is called InkScape (http://www.inkscape.org).
It's opensource, and while it's intended primarily for editing SVG vector-based images, it has two key features that are useful to us WPFers:
It can vectorize (i.e. "trace") raster images like bitmaps and jpegs, albeit not as well as one would hope, and
It can export the vector image as XAML
You'll invariably find that you get better results from loading vector formats (like SVG, EMF, WMF, etc) and saving to XAML, than if you try to convert a bitmap/jpeg... simply because the process of vectorizing a raster image is error prone at best. So if you want to bring a company logo into XAML, try to get hold of the source files used to create the logo (perhaps done in Illustrator?) and import that into InkScape.
If this post is helpful, please be kind and give it a one-up.
Jasema is a terrific tool right for the job.
Also, don't be shy to use Blend - it is somewhat more difficult to use (drawing shapes using pen) but it gets easier pretty fast. Switch on gridlines and optionally snap to them for good results.
What both Jasema and Blend are lacking, is the ability to easily create shapes with a central symmetry (like stars), so I took parts from Jasema and created my own tool (named Radius) that works a bit like a combination of a ruler and compass.
I have a good idea but you're png, bmp, jpg or other non vector file is must be very simple because we need best scan results and only use inkscape.
Step: Drag and drop your file workspace on Inkscape, download free.
Tip: If your image is color white, Top menu item File->Document Properties-> heck Checkerboard Background and if you want uncheck Page border show.
Step: Top menu item Path-> Trace Bitmap-> Mode check what you want property, i usually use color property and if your file is png check Remove Background then click OK, then wait again Ok button is Enable and close window.
Step: Now you have a two layer, top layer vektor file and bottom layer your file. Select vector file and top menu item Edit-> XML Editor-> select svg path and look side column, d name propery in your data path value.
But this method may not always work or may not give the desired results and draw your own shapes with the scape so you can get the path data from the XML editor.
Example, my first tests this like:
and after working on it some more:
I've solved my problem (export an image as XAML) using Microsoft Expression Design 4 (Free Version). I've downloaded from the link
http://www.microsoft.com/en-us/download/confirmation.aspx?id=36180
As input, I had Adobe Ilustrator files.
Adobe Illustrator / CorelDraw is perhaps the best tool out there for these operations that I have used.
Personally, I prefer illustrator for on-screen media. These tracings can be exported into several formats such as EPS, SVG, AI, or even XAML (with this plugin)
Best of Luck !!!!
I have recently been struggling with this myself. I had a set of icons done in data and needed to update them to look nicer.
I tried everything, manually typing them out. drawing in svg, converting svg to xaml.
in the end i found a list of open source icons from google material icons.
I then used this to convert from the svg files to data
https://github.com/BerndK/SvgToXaml
It works well but not for the icons i drew myself.
I decided to place all the icons data i convert into an app i built myself that will give you the data and a preview of the icon. feel free to use and contribute. I will keep updating as much as i can.
https://github.com/sgreaves1/XamlIcons
Convert your image from png to svg in online converter, then drop file into this site http://inloop.github.io/svg2android/ and you will see pathData of your image like below shown in my image.
When designing a website, what do you consider the best image format to use for a particular task?
I always find myself in a dilemma when trying to figure out what format to use for a specific task...like for example, should I use .jpg all round? or, when and why should I use a .png?
For example, taking Amazon's website, they use .jpg for product images (Example), .gif for this transparent pixel (Example) and .png for their CSS Sprites (Example)
On the other hand, Play.com use a .gif for their website logo (Example), but use .jpg for their website products (like Amazon) (Example) and as far as their main page goes, they dont have any .pngs on it.
So what formats should I use for my websites? and why should I use them?
[UPDATE]
Thanks CruellO for this link for explaining the differences, and also Dustin for giving reasons on what to use.
You should be aware of a few key factors...
First, there are two types of compression: Lossless and Lossy.
Lossless means that the image is made smaller, but at no detriment to the quality. Lossy means the image is made (even) smaller, but at a detriment to the quality. If you saved an image in a Lossy format over and over, the image quality would get progressively worse and worse.
There are also different colour depths (palettes): Indexed color and Direct color.
With Indexed it means that the image can only store a limited number of colours (usually 256) that are chosen by the image author, with Direct it means that you can store many thousands of colours that have not been chosen by the author.
BMP - Lossless / Indexed and Direct
This is an old format. It is Lossless (no image data is lost on save) but there's also little to no compression at all, meaning saving as BMP results in VERY large file sizes. It can have palettes of both Indexed and Direct, but that's a small consolation. The file sizes are so unnecessarily large that nobody ever really uses this format.
Good for: Nothing really. There isn't anything BMP excels at, or isn't done better by other formats.
GIF - Lossless / Indexed only
GIF uses lossless compression, meaning that you can save the image over and over and never lose any data. The file sizes are much smaller than BMP, because good compression is actually used, but it can only store an Indexed palette. This means that there can only be a maximum of 256 different colours in the file. That sounds like quite a small amount, and it is.
GIF images can also be animated and have transparency.
Good for: Logos, line drawings, and other simple images that need to be small. Only really used for websites.
JPEG - Lossy / Direct
JPEGs images were designed to make detailed photographic images as small as possible by removing information that the human eye won't notice. As a result it's a Lossy format, and saving the same file over and over will result in more data being lost over time. It has a palette of thousands of colours and so is great for photographs, but the lossy compression means it's bad for logos and line drawings: Not only will they look fuzzy, but such images will also have a larger file-size compared to GIFs!
Good for: Photographs. Also, gradients.
PNG-8 - Lossless / Indexed
PNG is a newer format, and PNG-8 (the indexed version of PNG) is really a good replacement for GIFs. Sadly, however, it has a few drawbacks: Firstly it cannot support animation like GIF can (well it can, but only Firefox seems to support it, unlike GIF animation which is supported by every browser). Secondly it has some support issues with older browsers like IE6. Thirdly, important software like Photoshop have very poor implementation of the format. (Damn you, Adobe!) PNG-8 can only store 256 colours, like GIFs.
Good for: The main thing that PNG-8 does better than GIFs is having support for Alpha Transparency.
Important Note: Photoshop does not support Alpha Transparency for PNG-8 files. (Damn you, Photoshop!) There are ways to convert Photoshop PNG-24 to PNG-8 files while retaining their transparency, though. One method is PNGQuant, another is to save your files with Fireworks.
PNG-24 - Lossless / Direct
PNG-24 is a great format that combines Lossless encoding with Direct color (thousands of colours, just like JPEG). It's very much like BMP in that regard, except that PNG actually compresses images, so it results in much smaller files. Unfortunately PNG-24 files will still be much bigger than JPEGs, GIFs and PNG-8s, so you still need to consider if you really want to use one.
Even though PNG-24s allow thousands of colours while having compression, they are not intended to replace JPEG images. A photograph saved as a PNG-24 will likely be at least 5 times larger than the equivalent JPEG image, with very little improvement in visible quality. (Of course, this may be a desirable outcome if you're not concerned about file size, and want to get the best quality image you can.)
Just like PNG-8, PNG-24 supports alpha-transparency, too.
JPEGs are for photos. I see JPEGs with text in them occasionally and they just look awful. Text is best for text, otherwise use PNG.
If it's not a photo, but you want a graphic of it, use a PNG. A PNG is almost always smaller than the equivalent gif and will not lose quality like a JPEG file. A PNG equivalent of a JPEG will typically be a lot larger (assuming it's photorealistic). There may be times where this is still desirable.
PNG does allow for 8-bits of transparency, but if you have to support IE, you'll find that they continually refuse to support that correctly. They do support a single bit of transparency in an 8-bit image (essentially the same as gif) as far as I know. There are also numerous hacks to get 8-bit transparency to work in IE. I've never bothered, myself.
In summary:
Photos → jpg
!Photos → png
PNG can be used when:
You need transparency (either 1-bit or alpha transparency)
Lossless compression will work well (such as a flat-style icon or logo)
JPEG can be used when:
Lossless compression will not work well (such as a photograph)
GIF can be used when:
Animation is necessary, and video is not possible (though you should really try and use video; animated GIFs are poor quality and very inefficient)
Despite myths to the contrary, PNG outperforms GIF in all like for like comparisons. PNG is capable of every image mode of GIF apart from animation, and when using the same image mode, PNG will have better compression due to its superior DEFLATE algorithm compared to LZW. PNG is also capable of additional modes that GIF cannot do, such as 24 bit color, and multi-bit transparency (alpha transparency). Note that multi-bit transparency used to be a problem back when people used IE6.
PNG modes include (this is just a small subset)
Palette colour of 2 to 256 colors (like GIF)
Palette colour of 2 to 256 colors, with transparent color (like GIF)
True color (24 bit color)
True color with alpha channel (24 bit color + 8 bit transparency)
For best compression in PNG for the web, always use a palette mode. If you find PNG files are larger than the equivalent GIF files, then chances are you're saving the PNG in 24 bit color and the GIF in palette mode (because saving a full color GIF always requires translation to palette mode). Try converting the image to palette mode before saving in both cases.
PNG also has other modes such as palette color with alpha transparency in the palette. Modes such as this work in browsers but software like Photoshop have (or once had) problems with creating or working with them due to not supporting those image modes.
If you are storing or presenting a large number of images the new Google WebP format might be worth considering as it is 25% smaller than PNG/JPG.
Note this is not supported by all browsers at the moment.
NB. This came out in 2010 after this question was posted.
JPEG FILE FORMAT
Great for images when you need to keep the size small
Good option for photographs
Bad for logos, line art, and wide areas of flat color
GIF FILE FORMAT
Great for animated effects
Nice option for clip art, flat graphics, and images that use minimal colors and precise lines
Good option for simple logos with blocks of colors
PNG FILE FORMAT
Lossless
Excellent choice when transparency is a must
Good option for logos and line art
Not supported everywhere
You can see this infographics for more detailed information, Image File Types: When to use JPEG, GIF & PNG
Does anyone know of any way to convert a simple gif to xaml? E.G. A tool that would look at an image and create elipses, rectangles and paths based upon a gif / jpg / bitmap?
Inkscape can trace bitmaps, and can save directly to XAML. And, it happens to be free. I've used it to trace a lot of bitmaps and it's worked really well for me.
Illustrator has a trace tool which will do this
a cheaper option might be
http://vectormagic.com
it will export a svg that you should be able to convert to xaml
A combination of Vector Magic followed by ViewerSVG produces the best quality results for me.
With this online converter you can convert an image to SVG Format. then download Converted File and open it in a text File Editor then you can easily copy path data
image.online-convert