I want to remove background unnecessary greyed pixels in above image.
May i know how to do that.
Quick and dirty with ImageMagick:
convert 9AWLa.png -blur x1 -threshold 50% out.png
Somewhat better, still with ImageMagick:
convert 9AWLa.png -morphology thicken '1x3>:1,0,1' out.png
Updated Answer
It is rather harder to keep the noisy border intact while removing noise elsewhere in the image. Is it acceptable to trim 3 pixels off all the way around the edge, then add a 3 pixel wide black border back on?
convert 9AWLa.png -morphology thicken '1x3>:1,0,1' \
-shave 3x3 -bordercolor black -border 3 out.png
Some methods that come to my mind are
If the backgroud is gray color rather than sparse black dots then you can convert the image in binary by thresholding it with proper value of grayscale. i.e. all values above particular values of pixel are white and all values below that are black. Something like this.
Another thing you can do is first smoothing the picture my some filter like mean or median filter and then converting into binary presented in previous point.
I think in this way the unnecessary background can be removed
Related
I need to take an image and append a mirror image of itself to the right (or left). It's got to do with mapping surfaces around spheres where some surface maps do not have left and right sides that "match up". (Digression: Is there is a name for the characteristic of an image whose right and left sides can be placed next to each other, wrapped around a cylinder or sphere, seamlessly?). Appending a mirror image to itself is a quick and dirty way to fix this problem in an environment where the image is chaotic and the viewer won't notice the trick being played.
This ImageMagick command almost does the trick but the problem is, it extends the image vertically as well as horizontally but leaves the vertical extent as an empty transparency. I just want a horizontal, mirror image extension:
convert original.jpg -background transparent -extent 200% \( +clone -flop \) -composite mirror.jpg
I need the -extent option to only extend in the horizontal direction. The ImageMagick documentation doesn't cover percentage values for -extent, only ratios like -extent 4:3 or absolute dimensions like -extent 800x600 but -extent 200% isn't in the documentation. Something like -extent 200% right is what I want. I have many images to run this transformation on and do not want to manually enter dimensions.
I'm trying to make a capcha solver, but I have ran into some trouble. The captcha that I am trying to solve has different coloured backgrounds.
I need to convert it to black text on white background so that it could easily be recognised by tesseract-ocr
I have tried
convert *.png -threshold 50% *.png which only shows some of the digits.
The problem with simple 50% thresholding is that both colours may be lighter than 50% grey and will therefore come out as white. Or, conversely, both colours may be darker than mid-grey and therefore bith come out as black.
You need to do a 2-colour quantisation to get just 2 colours, then go to greyscale and normalize so the lighter colour goes white and the darker one goes black. I am not near a computer, to test, but that should be:
convert input.png -colors 2 -colorspace gray -normalize result.png
Now, you will find some images are inverted (black on white instead of white on black), so you can either test the top left corner pixel and if it is white, then invert the image. Or, you could get the mean of the image and if it is more than 0.5 that would indicate that the image is largely white and therefore needs inverting.
Invert with:
convert input.png -negate output.png
Get top-left pixel with:
convert image.png -format '%[pixel:p{0,0}]' info:-
Get mean value with:
convert image.png -format "%[mean]" info:-
I have an PNG with an alpha channel. First I want to find all elements in the png, then I want to stretch the last color on the border about 5 to 10 pixels out
The stretching has to be in all directions from the center of each object on the image (like triangle, rectangle...)
It is important that I keep the color of each pixel on the edge
Is this possible? Goal is in the future to automate the process with ImageMagick.
I have had a play with distort and it is probably the way to go but needs more investigation. I was working on a smaller image and the code is basically a proof of concept.
I think edge is the key option and with this example I reduced the size of the resized image all round by 20px in the distort.
I do not know how you would get the angled edges though.I know you do not want to distort the original but it may give you some ideas as to how to get the result you want.
convert "1.png" -trim -matte -virtual-pixel edge -mattecolor none -interpolate Spline +distort BilinearForward "0,0 20,20 400,0 380,20 400,95 380,55 0,95 20,55" -trim +repage "result.png"
I am not quite sure what is going on at the edges of your image, but this should get you started...
First, I trim off any transparent edges (with -trim) so we get to the actual pattern you seek to extend. Then clone the image and dispose of everything except the top row of pixels (with -crop). Then scale that row up till it is 800 pixels tall. Then exchange the tall top row with the original image in the processing order (using +swap) and append the original image below the height-extended top row.
convert cells.png -trim +repage \( +clone -crop x1+0+0 -scale x800! \) +swap -append result.png
Assume I have an original image (gray backgorund) with a black circle a bit down to the right (not centered), and the minimum space from any edge of the circle to the edge is, lets say, 75px. I would like to trim the same amount of space on all sides, and the space should be the maximum space possible without cropping the actual object in the image (area in magenta in image). Would love to hear how this could be solved.
Thanks in advance!
If I understand the question correctly, you want to trim an image not based on minimum bounding rectangle, but outer bounding rectangle.
I would do something like this..
Given I create an image with.
convert -size 200x200 xc:gray75 -fill black -draw 'circle 125 125 150 125' base.png
I would drop the image to a binary edge & trim everything down to the minimum bounding rectangle.
convert base.png -canny 1x1 -trim mbr.png
This will generate mbr.png image which will also have the original page information. The page information can be extracted with identify utility to calculate the outer bounding rectangle.
sX=$(identify -format '%W-(0 %X)-%w\n' mbr.png | bc)
sY=$(identify -format '%H-(0 %Y)-%h\n' mbr.png | bc)
Finally apply the calculated result(s) with -shave back on the original image.
convert base.png -shave "${sX}x${sY}" out.png
I assume that you want to trim your image (or shave in ImageMagick terms) by minimal horizontal or vertical distance to edge. If so this can be done with this one liner:
convert circle.png -trim -set page "%[fx:page.width-min(page.width-page.x-w,page.height-page.y-h)*2]x%[fx:page.height-min(page.width-page.x-w,page.height-page.y-h)*2]+%[fx:page.x-min(page.width-page.x-w,page.height-page.y-h)]+%[fx:page.y-min(page.width-page.x-w,page.height-page.y-h)]" -background none -flatten output.png
This may look complicated but in reality isn't. First trim the image. The result will still have stored information on page geometry including original width, height and actual offsets. With this info I can set the page geometry (correct width & height and new offsets) using ImageMagick FX expressions. Finally, flattening the image will produce desired output.
I want draw boundery box around the text like this image Image 2
from this Image 1. Can anyone suggest me a good way to do this or some algorithm or turorial anything?.
As you haven't suggested a tool, I will use ImageMagick straight at the command line as it is installed on most Linux distros and is available for OSX and Windows. It also has PHP, Perl, Python and .Net bindings.
So, as your background is uniform (ish) you can just use trim to trim it off:
convert image.jpg -fuzz 20% -trim result.jpg
Now you can add a border like this:
convert result.jpg -bordercolor black -border 5 result.jpg
Except you want the other grey background to be retained so that doesn't work for you. So, instead of actually trimming, we can ask ImageMagick where it "would" trim but to not actually do it like this:
convert image.jpg -fuzz 20% -format %# info:
81x22+1+14
So, we know it would make a 81x22px box starting 1 pixel in from the left and 14 pixels down from the top, so we'll just draw a rectangle there instead of trimming it:
convert image.jpg -fill none -stroke black -draw "rectangle 1,14 82,36" result.jpg
Or, if you want the outline fatter:
convert image.jpg -fill none -stroke black -strokewidth 5 -draw "rectangle 1,14 82,36" result.jpg
For a uniform background, a simple solution would be to identify all of the pixels that do not match the background color and then find the minimum and maximum indices in each axis of those pixels to define a rectangle.
For instance, if you were using Matlab, this might resemble:
Use 'find' to identify non-background pixels (e.g. linearIndices = find(~(image1 == background)) where background is either a hard coded set of RGB values corresponding to the background pixels or a set of RGB values identified by the mode of the image.
'Find' will return linear indices rather than subscripts (i.e. bottom right corner of a 3x3 matrix is 9, not [3,3]) so use 'ind2sub' to convert to subscripts (e.g. [I,J] = ind2sub(imageSize, linearIndices)
Use 'max' and 'min' to find range in x and y (e.g. rangeX = [min(I) max(I); rangeY = [min(J) max(J)])
Change pixels along min and max indices to border color. For instance, image1 ( rangeX(1), rangeY(1):rangeY(2) ) = boxColour (where boxColour is the RGB values of the colour you want the box to be) would draw the left border of the box. Repeat this process for the three other borders and you're done.
Of course this approach only works if the background is completely uniform. It also assumes you only want to draw a border that is one pixel thick.
While the function recommendations correspond specifically to Matlab functions, the thought process behind those functions could likely be ported elsewhere.