I have a raw iPad screenshot and I would like to place a "perfect battery top bar" top on it. I believe I can use $ composite -gravity to accomplish this, but I am new to imagemagick and its massive library... any tips on how to tackle this problem?
Just use composite and check that the topbar has the same width as the image. In composite parameter 3 + 4, are the x and y offset. Since you want it aligned on top, use 0, 0.
<?php
header('Content-type: image/jpeg');
$topbar = new Imagick("/var/www/topbar.png"); //600*19px
$tapir = new Imagick("/var/www/tapir.jpg"); // 600*400px
$tapir->compositeImage($topbar, Imagick::COMPOSITE_OVER, 0, 0);
echo $tapir;
?>
Related
I am quite a noob when it comes to image processing. I choosed OpenCV to make my first steps. I was searching for a WYSIWYG editor to play around with the features OpenCV offers but I couldn't find.
My current problem is to detect the horizontal and vertical black lines in this picture going from most left to most right and from most top to most bottom:
I found out I can use HoughLinesP for this but the only parameter I am sure it is correct is the the minLineLength of the line. Actually it doesn't find any lines. I am reading the image as a grayscaled image but I am not sure if I need to make use of Canny before applying it to HoughLinesP.
Thanks for help.
Here is some C# code:
var image = CvInvoke.Imread(filePath, Emgu.CV.CvEnum.ImreadModes.Grayscale);
var lines = CvInvoke.HoughLinesP(image, 1, 1, 0, image.Height);
As #Micka mentioned I should invert the image and I tried further steps to make it even simpler I started with a simple cross picture:
var image = CvInvoke.Imread("cross.png", Emgu.CV.CvEnum.ImreadModes.Grayscale);
CvInvoke.BitwiseNot(image, image);
var lines = CvInvoke.HoughLinesP(image, rho: 1, theta: 1, 0, image.Height - 1);
But it detects only one line of length 8 but it should be 9 pixels long.
Setting
Suppose we have a list of N elements of which an element can either be a path to an image (e.g. a.jpg) or NULL indicating that a file is missing.
Example (N = 6): a.jpg,NULL,c.jpg,NULL,NULL,f.jpg
All mentioned images (a.jpg, c.jpg, f.jpg) are guaranteed to have the same resolution.
Task
Create a fixed-width montage (e.g. out.jpg) in which NULL values are replaced with black images whose resolutions are consistent with the common resolution of a.jpg, c.jpg, f.jpg. I would like to abstain from creating an actual black.jpg and would prefer to create the image on-the-fly as needed.
Using ImageMagick's "montage" command, if your images are known dimensions so you can include that in the command, and if you can generate a text file "list.txt" of the image files and put "xc:black" on each line that has no image like this...
image00.png
image01.png
image02.png
image03.png
image04.png
xc:black
image06.png
image07.png
xc:black
xc:black
image10.png
image11.png
You can run the ImageMagick "montage" command something like this...
magick montage #list.txt -tile 3x4 -geometry 160x160+3+3! out.png
The "#" in front of the name of the text file tells IM to read the input images from there. The "-tile" describes how many columns and rows will be in the result. The "-geometry" setting is where you put the dimensions of the images and the spacing between columns and rows. The "xc:black" images are single black pixels, but the exclamation point forces them to the W and H dimensions in the "-geometry" argument.
That will create black images everywhere you have "xc:black" in the list. If you want to fill between the spaces with black also, add "-background black" to the command.
That works for me with IMv7 and "magick montage ..." For IMv6 you just use "montage". I'm pretty sure everything else about the command would work the same way.
I imagine this is a shot in the dark, but is it possible to have a vector file of a shape (in this case a hexagon with rounded corners), and pass an image through some code and have it coming out cropped in the shape of that vector?
I'm attempting to utilize hexagons in my design and have gone through every page I possibly can. I've seen the many HTML and CSS solutions, but none of them achieve what I'm looking for flawlessly.
Another idea I have is maybe overlaying a transparent hexagon shape with white corners on top of the existing image with imagemagick, and then going through and making any white transparent. Thoughts?
I don't have any code for cropping in the shape of a vector file, but here's what I have for overlaying an outline of the shape I want on top of the other picture:
imgfile = "public/" + SecureRandom.uuid + ".png"
SmartCropper.from_file(art.url(:original)).smart_square.resize(225,225).write(imgfile)
overlay = Magick::Image.read("app/assets/images/overlay.png")
img = Magick::Image.read(imgfile)
img.composite(overlay,0,0, Magick::OverCompositeOp)
Right now it's giving me an undefined method error for composite, which is strange because I've followed some other stack overflow questions using the same thing in their models.
Any help is appreciated!
You have fallen for a common ImageMagick trap - the objects you get from the .read method are not Magick::Image objects but Magick::ImageList ones, and for most image types you want the first item from the list.
Without knowing how you have set up your overlay.png file, it is difficult to tell what the best composite option is. However, in a similar situation I found CopyOpacityCompositeOp to be useful, and to have the overlay's transparency control the transparency in the final image.
I tested the following code and it looks like it would do what you want if overlay.png was set up that way:
require 'smartcropper'
imgfile = "test_square.png"
SmartCropper.from_file( 'test_input.png' ).
smart_square.resize( 225, 225 ).write( imgfile )
overlay = Magick::Image.read( 'overlay.png' ).first
img = Magick::Image.read( imgfile ).first
img.composite( overlay, 0, 0, Magick::CopyOpacityCompositeOp ).
write( "test_result.png" )
Instead of reading overlay from a file, you could create it using Magick::Draw like this:
overlay = Magick::Image.new( 225, 225 ) do |i|
i.background_color= "Transparent"
end
gc = Magick::Draw.new
gc.stroke('white').stroke_width(10)
gc.fill('white')
gc.polygon(97.5, 26.25, 178.5, 73.125, 178.5, 167,
97.5, 213.75, 16.5, 167, 16.5, 73.125)
gc.draw( overlay )
NB That's a hexagon, but I've not bothered centering it.
I've got an image that i'd like to 'pad' with white space and centre.
In most cases I need to resize the image from 16 or 32 pixels up to 32 pixels.
If the image is 16 pixels, I want to add 8px of white space on each side, making it a 32 pixel image (with the original floating in the middle).
If it's a 32 pixel image, then nothing changes.
I'm using RMagick to do the conversion:
image.change_geometry!("#{size}x#{size}") { |cols, rows, img|
newimg = img.extent(cols, rows)
newimg.write("#{RAILS_ROOT}#{path}/#{name}.png")
}
Which is working OK, but the smaller images are in the top left of the new image, not centred.
I was looking at the gravity setting, it seems to be what I need, but I can't work out how to specify it in the call?
Thanks in advance.
Check the implementation of the following carrierwave function
http://rubydoc.info/gems/carrierwave/0.5.1/CarrierWave/RMagick#resize_and_pad-instance_method
This is a version of the above method by using only RMagick dependency
require 'RMagick'
include Magick
module Converter
def self.resize_and_pad(img, new_img_path, width, height, background=:transparent, gravity=::Magick::CenterGravity)
img.resize_to_fit!(width, height)
new_img = ::Magick::Image.new(width, height)
if background == :transparent
filled = new_img.matte_floodfill(1, 1)
else
filled = new_img.color_floodfill(1, 1, ::Magick::Pixel.from_color(background))
end
# destroy_image(new_img)
filled.composite!(img, gravity, ::Magick::OverCompositeOp)
# destroy_image(img)
# filled = yield(filled) if block_given?
# filled
filled.write new_img_path
end
end
The extent() method takes two more parameters, x & y offsets, which is where the image will be placed within the extent. If you're asking extent for a 100x100 image, for example, and your original is only 50x50, you'd do img.extent(100, 100, 25, 25) -- which would set the image to start at offset 25,25 (thus centering it).
NOTE: There's some issue with extent expecting to use negative offset values (in which case you'd want to do -25, -25) -- check this:
why is the behavior of extent (imagemagick) not uniform across my machines?
If I have a image with, let's say squares. Is it possible to remove all shapes formed by 10 (non white) pixels or less and keep all shapes that is formed by 11 pixels or more? I want to do it programmatically or with a command line.
Thanks in advance!
Possibly an algorithm called Erosion may be useful. It works on boolean images, shrinking all areas of "true" removing one layer of their surface pixels. Apply a few times, and small areas disappear, bigger ones remain (though shrunken). De-shrink the survivors with the opposite algorithm, dilation (apply erosion to the logical complement of the image). Find a way to define a boolean images by testing if a pixel is inside an "object" however you define it, and find a way to apply the results to the original image to change the unwanted small objects to the background color.
To be more specific would require seeing examples.
Look up flood fill algorithms and alter them to count the pixels instead of filling. Then if the shape is small enough, fill it with white.
There are a couple of ways to approach this. What you are referring to is commonly called Despeckle in Document Imaging Applications. Document scanners often introduce a lot of dirt and noise into an image during scanning and so this must be removed removed to help improve OCR accuracy.
I assume you are processing B/W images here or can convert your image to B/W otherwise it becomes a lot more complex. Despeckle is done by analysing all the blobs on the page. Another way to decide on blob size is to decide on width, height and number of pixels combined.
Leptonica.com - Is an Open Source C based library that has the blob analysis functions you require. With some simple check and loops you can delete these smaller objects. Leptonica can also be compiled quite easily into a command line program. There are many example programs and that is the best way to learn Leptionica.
For testing, you may want to try ImageMagick. It has a command line option for despeckle but it has no further parameters.
http://www.imagemagick.org/script/command-line-options.php#despeckle
The other option is to look for "despeckle" algorithms in Google.
ImageMagick, starting from version 6.8.9-10, includes a -connected-components option which can be used to do what you want, however from the example provided in the official website, it is not immediately obvious how to actually obtain the original image minus the removed connected components.
I'm almost sure there is a simpler way, but I did it via a clunky script performing a series of steps:
First, I ran the command from the connected components example:
convert in.png \
-define connected-components:verbose=true \
-connected-components 8 out.png
This produces output in the following format:
Objects (id: bounding-box centroid area mean-color):
(...)
181: 9x9+1601+916 1605.2,920.2 44 gray(0)
185: 5x5+1266+923 1268.0,925.0 13 gray(0)
274: 5x5+2276+1661 2278.0,1663.0 13 gray(255)
Then, I used awk to filter only the lines containing an area (in pixels) of black components (mean-color gray(0) in my image) smaller than my threshold $min_cc_area. Note that connected-components has an option to filter components smaller than a given area, but I needed the opposite. The awk line is similar to the following:
{if ($4 < $min_cc_area && $5=="gray(0)") { print $2 }}
I then proceeded to create a command-line for ImageMagick where I drew white rectangles on top of these connected components. The -draw command expects coordinates in the form x1,y1 x2,y2, so I used awk again to compute the coordinates from the ones in the format [w]x[h]+x1+y1 given by -connected-components:
awk '{print "white fill rectangle " $3 "," $4 " " $3+$1-1 "," $4+$2-1 }'
Finally, I ran the created ImageMagick command-line to create a new image combining all the white rectangles on top of the original one.
In the end, I got the following script:
# usage: $0 infile min_cc_area outfile
infile=$1
min_cc_area=$2
outfile=$3
awk_exp="{if (\$4 < $min_cc_area && \$5==\"gray(0)\") { print \$2 }}"
draw_rects=""
draw_rects+=$(convert $infile -define connected-components:verbose=true \
-connected-components 8 null: | \
awk "$awk_exp" | tr 'x+' ' ' | \
awk '{print " rectangle " $3 "," $4 " " $3+$1-1 "," $4+$2-1 }')
convert $infile -draw "fill white $draw_rects" $outfile
Note that this solution may erase black pixels near the removed CC's, if they insersect the bounding rectangle of the removed component.
You want a connected components labeling algorithm. It will scan through the image and give every connected shape an id number, as well as assign every pixel an id number of what shape it belongs to.
After running a connected components filter, just count the pixels assigned to each object, find the objects that have less than 10 pixels, and replace the pixels in those objects with white.
If you can use openCV, this piece of code does what you want (i.e., despakle). You can play w/ parameters of Size(3,3) in the first line to get rid of bigger or smaller noisy artifacts.
Mat element = getStructuringElement(MORPH_ELLIPSE, Size(3,3));
morphologyEx(image, image, MORPH_OPEN, element);
morphologyEx(image, image, MORPH_CLOSE, element);
You just want to figure out the area of each components. So an 8-direction tracking algorithm could help. I have an API solve this problem coded in C++. If you want, send me an email.