Here's the original image I'm trying to remove background from:
I am trying to use imagemagick to remove the background from an image. When the image has a white product, my script doesn't work well. It removes the white from inside the product also. In brief I'm trying to do the following
create a mask image (replace background pixels with white with fuzz and threshold)
apply the mask over the original image to generate the output
If I use a fuzz factor of 0, like shown below, i get the background removed, but it creates a nasty halo around it. What can be done here?
I would take advantage of HSL colorspace, and create an alpha mask from the lightness channel.
convert tshirt.jpg \( \
+clone -colorspace HSL -separate \
-delete 0,1 -fx 'u>0.975?0:1' \) \
-compose CopyOpacity -composite \
out.png
I would go for a simple threshold to pick out the white and then some sort of filtration to remove the noise/ragged edges. So, for example
convert shirt.jpg -threshold 99.99% -negate result.jpg
which gives this:
Then apply some median filtering to smooth it:
convert shirt.jpg -threshold 99.99% -median 5 -negate result.jpg
or maybe a bigger filter:
convert shirt.jpg -threshold 99.99% -median 11 -negate result.jpg
which gives this
Alternatively, you may get on better with an erosion and a dilation...
convert shirt.jpg -threshold 99.99% -negate \
-morphology erode diamond:3 \
-morphology dilate diamond:3 result.jpg
You may like to use Anthony Thyssen's flicker_compare to flicker between the input and result image to see what you have got, see here.
./flickercompare -o flick.gif shirt.jpg result.jpg
Related
I have the following image:
What I want is to preserve only red color and desaturate
every other color into grayscale. Resulting in this:
How can I do that with Imagemagick command line?
I tried this but failed:
convert original.png \( -clone 0 -transparent red -alpha extract -transparent black \) redonly.png
Here is one way, though not perfect, using ImageMagick. I specify hue=0 deg for red and tolerance=25 deg both in range 0 to 360.
Input:
hue=0
tolerance=25
toler=`convert xc: -format "%[fx:(100*$tolerance/360)]" info:`
hueval=`convert xc: -format "%[fx:50-$hue]" info:`
thresh=`convert xc: -format "%[fx:100-$tolerance]" info:`
convert tomato.jpg \
\( -clone 0 -colorspace gray -colorspace sRGB \) \
\( -clone 0 -colorspace HSL -channel 0 -separate +channel \
-evaluate AddModulus ${hueval}% \
-solarize 50% -level 0x50% \
-threshold $thresh% \) \
-swap 0,1 -alpha off -compose over -composite \
result.jpg
Also not perfect, but fairly easy to understand. Basically, you could use the fx operator to inspect the Hue of each pixel and, depending on its Hue/colour, return either the original pixel or its greyscale equivalent.
So, as a first stab, you might do this to replace all pixels exhibiting a high Hue value with their greyscale (lightness) equivalent:
magick ripe.jpg -fx "(u.hue<0.1)? u : u.lightness" result.jpg
Then you might realise that red Hues wrap around at 0/360 degrees on the Hue circle, so you could do:
magick ripe.jpg -fx "(u.hue<0.1)||(u.hue>0.9)? u : u.lightness" result.jpg
Explanation
There are a couple of things going on here. Firstly, the -fx operator is a very low-level, extremely powerful (and sadly rather slow because it is interpreted) way of running a piece of "code" on every pixel in the image. Secondly, I am running a ternary operator with the format:
condition? valueA : valueB
so I am testing a condition for every pixel, and if true I return valueA, and if false I return valueB. When I refer to u and u.hue and u.lightness, the u means the first image in my command - I could load two images and use features of the first to select features of the second, then I would use u and v to differentiate. Finally, the values are scaled on the range [0,1] so I don't test for "Hue>350 in the range [0,360]", instead I test for Hue>0.9 as a sloppy equivalent - I guess I could have used Hue>(350/360). Note that you can make the expression arbitrarily complicated and also put it in a separate file to re-use it like this:
magick ripe.jpg -fx #DeSatNonRed.fx result.jpg
DeSatNonRed.fx might look something like this:
hueMin=350/360;
hueMax=20/360;
(hue>hueMin) || (hue<hueMax) ? u : u.lightness
Note that, in the general case, you should also really consider Saturation when looking at Hues, which you can add in above, but which I omitted for clarity, and because your image is almost fully saturated anyway.
Keywords: Image processing, ImageMagick, low-level fx operator, ternary, pixel-by-pixel, evaluate, expression.
How do I adjust the color ratio of a gradient?
I currently use the following to create my gradient.
convert -size 200x600 gradient:none-black output.png
Although at least one acceptable solution has been provided, here are a couple other ideas...
Example 1: This command creates a red-blue gradient of the finished dimensions, crops it into a top and bottom half, resizes them to 40 and 60 percent of the input height, and appends them back to make a single image. What started as the color at the exact vertical center is now at 40% down from the top with clean gradients going up and down from there.
convert -size 200x600 gradient:red-blue -crop 1x2# \
\( -clone 0 -resize 100x40% \) \( -clone 1 -resize 100x60% \) \
-delete 0,1 -append result.png
That splits the gradient image into a top and bottom half, then inside parentheses it resizes each to the required proportion. After that it deletes the 50/50 crops from before the parentheses, appends the two resized remaining images, and writes the output.
Example 2: This next example starts by creating the red-blue gradient in the final dimensions, then sets variables to hold the top color, the exact middle color, and the bottom color.
Then inside the first parentheses it clones and crops the image to 60% its original height. It uses "-sparse-color" to fill that with a gradient from "color1" to "color2".
Inside the second parentheses it clones and crops the image to 40% its original height, and using "-sparse-color" again it fills it with a gradient from "color2" to "color3".
After creating those two gradients, delete the original, append the other two together, and write the output.
convert -size 200x600 gradient:red-blue \
-set option:color1 "%[pixel:p{0,0}]" \
-set option:color2 "%[pixel:p{0,h/2}]" \
-set option:color3 "%[pixel:p{0,h}]" \
\( -clone 0 -extent 100x60% \
-sparse-color barycentric "0,0 %[color1] 0,%[h] %[color2]" \) \
\( -clone 0 -extent 100x40% \
-sparse-color barycentric "0,0 %[color2] 0,%[h] %[color3]" \) \
-delete 0 -append result.png
Maybe you want this, where you get to the half-red/half-blue colour just 20% of the way down the height of the image. It is done by creating two gradients of different lengths and putting them back-to-back:
midcolour="rgb(127,0,127)"
convert -size 100x20 gradient:red-"$midcolour" \
-size 100x80 gradient:"$midcolour"-blue \
-append result.png
Another way is to put 3 single pixels together in a row and then resize that up to what you want. I know you want the middle to be 40% red and 60% blue, but, for ease of viewing, I'll make it lime green:
convert -size 1x1 xc:red xc:lime xc:blue -append -resize 100x100\! result.png
You would change lime to something like "rgb(100,0,155)".
I am not quite sure I understand. But if you want to start with 90% transparent (10% opaque black) and end with black. You can do:
convert -size 200x600 gradient:"graya(0,0.1)-black" output.png
graya means gray with alpha. So graya(0,0.1) is gray(0) or black with 0.1 fraction opacity, so 90% transparent.
Perhaps this is what you want:
Normal 50-50:
convert -size 200x600 gradient:red-blue red_blue1.png
60-40:
rr=`convert xc: -format "%[fx:0.6*255]" info:`
bb=`convert xc: -format "%[fx:0.4*255]" info:`
convert -size 200x600 gradient:"rgb($rr,0,$bb)-rgb(0,0,255)" red_blue2.png
Or perhaps this is what you want:
bb=`convert xc: -format "%[fx:0.1*255]" info:`
convert -size 200x600 gradient:"rgb(255,0,$bb)-rgb(0,0,255)" red_blue3.png
I have an Imagemagick bash shell script called, multigradient, which may do what you want. It allows you to create gradients of many colors each with stops to set where they start. For example:
multigradient -w 200 -h 600 -s "blue 0 red 80" -d to-top result.png
The first color must start at 0, but the direction can be many options. Here I go from bottom to top with pure blue at the bottom and pure red starting at 80 up from the bottom going to the top
(See)
I have a GIF image generated by a program where each output value is represented by its color via attached color palette. I need to replace one value, i.e. color from image with interpolated from neighboring pixels. Since I don't have possibility to alter programs output, I need to modify the output image. The resulting image will be saved in the PNG or GIF format.
I can easily extract (mask) all pixels that need repainting, since they have fixed color, but I was unable to find solution on how to replace a color of one/all pixels in imagemagick with interpolated color from neighboring pixels.
Is there a way to do this in imagemagick?
The raw values of the pixels are proportional to the physical value, so it would be great if the interpolation could be done on raw values that are then later transformed to the color via supplied color palette.
Attached image shows the original (left) and processed manually in GIMP (right).
One technique is to replace the offending color with the background, and then use a combination of erode & dilate morphology to remove the paths.
Given...
convert input.png \
-fill white -fuzz 10% -opaque black \
-morphology Erode Diamond \
-morphology Dilate Diamond \
output.png
It's not a true interpolate from nearest neighbors, but close. Also note the rounding errors across edges.
Updated
Or as Fred pointed out in the comments, just use -morphology Smooth Diamond instead of Erode + Dilate
convert input.png \
-fill white -fuzz 10% -opaque black \
-morphology Smooth Diamond \
output.png
Adding a bit to xenoid's suggestion, you want to create a mask image and use that to composite the median filter with the original, so that only the region about the line is changed. Using emcconville's image and ImageMagick:
convert img.png \
\( -clone 0 -statistic median 3x3 \) \
\( -clone 0 -fuzz 10% -fill white +opaque black -fill black +opaque white -negate \) \
-compose over -composite \
result.png
An alternate, but slightly longer approach, is to put the mask into the alpha channel of the filtered image and then composite it over the original, which produces exactly the same result:
convert img.png \
\( -clone 0 -statistic median 3x3 \) \
\( -clone 0 -fuzz 10% -fill white +opaque black -fill black +opaque white -negate \) \
\( -clone 1 -clone 2 -alpha off -compose copy_opacity -composite \) \
-delete 1,2 \
-compose over -composite \
result.png
Unfortunately, there is a slight dark residual to the upper left between the red and green. I tried increasing both the fuzz value and the filter size, but that did not seem to help. I am not sure why.
In ImageMagick convert, I can select a specific color with e.g. -opaque blue. How can I select all grayscale colors (e.g. #000000, #707070, #ffffff)?
Not sure what you are trying to do, but this may help. The greyscale pixels will have a saturation of zero, so that is probably the easiest way to identify them.
First, make a funky sample image:
convert -size 400x100 gradient:black-white -bordercolor red -border 80 image.png
Now make all grey areas (those with very low saturation) transparent:
convert image.png -alpha on -channel A -fx "saturation<0.01?0:1" result.png
Note
Note that the -fx operator is extremely powerful but notoriously slow because it is actually interpolated for each and every pixel. If your images are large, the following technique may be more appropriate.
Basically, I clone the image and convert the whole thing to HSL colorspace and separate the channels. Then I discard the Hue and Lightness channels so I am left with just the Saturation. I then threshold that and copy that back to the original image as the alpha channel. On a 2000x2000 pixel image, this method will run in under a second whereas the -fx method will require 5-6 seconds.
convert image.png \( +clone -colorspace hsl -separate -delete 0,2 -threshold 1% \) -compose copy-opacity -composite result.png
I have two images. One is background with no alpha. The other is a white cloud. The alpha of the cloud image is premultiplied with black. When I composite them the white cloud has black in it, so it looks grey instead of white like it should. I'm doing:
convert -gravity Center bg.tga whitecloud.tga -composite comp.tga
Is there a way to composite premultiplied images in ImageMagick, or does the image have to be non-premultiplied? Can I make a premultiplied image non-premultiplied using ImageMagick?
Update:
Ok, here are the images as TGA for download:
http://acatysmoof.com/posting/problems/imagemagick/premultiplication/bg.tga
http://acatysmoof.com/posting/problems/imagemagick/premultiplication/whitecloud.tga
http://acatysmoof.com/posting/problems/imagemagick/premultiplication/aftereffects.tga
http://acatysmoof.com/posting/problems/imagemagick/premultiplication/imagemagick.tga
and in the same order as jpgs to view in your browser:
I tried all the modes provided, but none of them create the same result as After Effects.
It would be easier if you showed your images, but try adding -compose lighten before -composite in your command, like this:
convert a.tga b.tga -compose lighten -composite out.tga
Basically that will make ImageMagick choose the lighter pixel of the two images at every point.
If that doesn't work, try other blending modes
for b in $(identify -list compose); do
convert -label "$b" bg.tga whitecloud.tga -compose $b -composite miff:-
done | montage - -tile 5x out.png
I am kind of thinking Atop, Dissolve, SrcAtop and SrcOver might be your friends but have a look full-size and see what floats your boat. That would be
convert a.tga b.tga -compose Atop -composite out.tga
Here is an Imagemagick command that does what you want:
convert -gravity Center whitecloud.tga -fx "u/max(u.a, 1/255)" bg.tga +swap -composite -fx "u*u.a" comp.tga
What's happening here?
-fx command #1: Convert whitecloud.tga from premultiplied alpha to "normal". The max() operator is a special case to avoid dividing by zero.
+swap command: Make bg.tga the first image and the revised whitecloud.tga the second.
-composite these two regular, non-premultiplied images.
-fx command #2: take the result, and return to a premultiplied alpha format.
This gives exactly the same result as After Effects.
Note that, as I wrote it, it only works for an opaque bg.tga. You'd need to do some extra work to handle a transparent background image.
If you want to duplicate the After Effects result, then I believe what you want to do in ImageMagick is the following -- composite the background image with a white image using the cloud as a mask:
convert bg.tga \( -clone 0 -fill white -colorize 100 \) whitecloud.tga -compose over -composite cloud_blue.tga
I have posted a JPG result, but my .tga result is the same.