How do you do the equivalent of this step in Photoshop.
https://gyazo.com/180a507c0f3c9b342fe33ce218cd512e
Supposed there are two contiguous objects in an image, and you want to create exact sized crops around each one and output as two files. (Generalize to N files)
You can do that with "Connected Component Analysis" to find the contiguous blobs.
Start Image
convert shapes.png -colorspace gray -negate -threshold 10% \
-define connected-components:verbose=true \
-connected-components 8 -normalize output.png
Sample Output
Objects (id: bounding-box centroid area mean-color):
0: 416x310+0+0 212.3,145.2 76702 srgb(0,0,0)
1: 141x215+20+31 90.0,146.2 26129 srgb(255,255,255)
2: 141x215+241+75 311.0,190.2 26129 srgb(255,255,255)
Notice how each blob, or contiguous object, is "labelled" or identified with its own unique colour (shade of grey).
So there is a header line telling you what the fields are followed by 3 blobs, i.e. one per line of output. The first line is the entire image and not much use. The second one is 141 px wide and 215 px tall starting at +20+31 from the top-left corner. The third one is the same size (because I copied the shape) and starts as +241+75 from the top-left corner.
Now stroke red around the final indicated rectangle - bearing in mind that rectangle takes top-left and bottom-right corners rather than top-left corner plus width and height.
convert shapes.png -stroke red -fill none -draw "rectangle 241,75 382,290" z.png
And crop it:
convert shapes.png -crop 141x215+241+75 z.png
And here is the extracted part:
If you want to generalise, you can just pipe the ImageMagick output into awk and pick out the geometry field:
convert shapes.png -colorspace gray -negate -threshold 10% -define connected-components:verbose=true -connected-components 8 -normalize output.png | awk 'NR>2{print $2}'
Sample Output
141x215+20+31
141x215+241+75
Related
This is an example PNG image:
it's 50x40 but enlarged here to see it better.
The hex of bottom left and bottom right pixels is F9E4B7
I need to know how many pixels there are on vertical edges from the bottom left and right with almost this color, like 1% fuzz because they are not all exactly F9E4B7 but some are very slightly different.
In this case it would be 20px of each side:
I'll mark the areas which need to be counted just to make it perfectly clear:
I also need to be able to count how many pixels are exactly F9E4B7, which in this case would be 15 left and 20 right, I'll mark the slightly different areas so it's clear where the counter needs to stop:
The way to do that in Imagemagick is to use fuzz to change all your pixels close to that color to white and the rest black. The crop the first or last column and use -fx to get the count from mean*width*height. So for example for the left full column of the whole image, one has
Unix Imagemagick 6 syntax:
convert tan.png -alpha off \
-fuzz 1% -fill white -opaque "#F9E4B7" -fill black +opaque white \
-gravity west -crop 1x+0+0 -format "%[fx:round(mean*w*h)]\n" info:
Windows Imagemagick Syntax:
convert tan.png -alpha off ^
-fuzz 1% -fill white -opaque "#F9E4B7" -fill black +opaque white ^
-gravity west -crop 1x+0+0 -format "%[fx:round(mean*w*h)]\n" info:
Result:
108
To get the right side, use -gravity east.
For exact count, use -fuzz 0
For Imagemagick 7, change convert to magick
I am trying to place a rotated image onto a blank canvas.
This is the command i am using:
convert "(" -size 1000x1000 xc:transparent ")" "(" "img.jpg" -virtual-pixel white -rotate -10.75 ")" -geometry +136+148 -composite "overlay.png" -geometry +0+0 -composite out.png
I would expect the image to appear at +136+148 rotated around its center. However, it appears to be rotated around its upper right corner instead.
I confirmed this in Photoshop:
This is the resulting image (using slightly different size but same parameters as my example command given here):
The 4 lines are the guides that mark the coordinates that define where the image sits. As you can see, the image is rotated -10.75 degrees. And the rotation center is the upper right corner.
Here i select the box at the correct coordinates in Photoshop:
And here i rotate it after setting the rotation point to the top right:
As you can see, the selection now matches the image as it was calculated by my convert command.
I have tried dealing with this for many hours. I tried switching to +distort and -distort and what not, but there i simply get either a cropped image or another wrongly positioned bounding box.
I don't know how to address this problem. What am i doing wrong? How can i tell -rotate to rotate my image around its center, not around the top right corner (why top right anyway?).
Thank you for your help!
The default gravity for offsetting is the northwest corner or top-left corner. The geometry offset you are using moves the top left corner of the padded rotated image after its background has been added and not the top left corner of the where the Input gets rotated. So I think that may be why you are not getting the expected result. ImageMagick -rotate does rotate about its center, but it fills the background out to make a complete rectangular image that is the bounding rectangle about the rotated image.
In ImageMagick, a better approach to what you did would be to use -gravity center and align the center of the rotated input image with the center of the transparent region in the overlay image.
Alternately, measure the 4 corners of your transparent region in the overlay and 4 corners of the input image and do a perspective or affine distortion to align the two.
Here is how to do it in bash unix syntax.
over1="122,186"
over2="466,118"
over3="510,345"
over4="166,411"
WxH=`convert -ping "Image.jpg" -format "%wx%h" info:`
ww=`echo "$WxH" | cut -dx -f1`
hh=`echo "$WxH" | cut -dx -f2`
ww=$((ww-1))
hh=$((hh-1))
in1="0,0"
in2="$ww,0"
in3="$ww,$hh"
in4="0,$hh"
convert overlay.png \
\( Image.jpg -virtual-pixel none +distort Perspective \
"$in1 $over1 $in2 $over2 $in3 $over3 $in4 $over4" \) \
-layers merge +repage \
out.png
See https://imagemagick.org/Usage/distorts/#perspective
Try using the offset geometry that aligns with the outer edges of your target area. That would be more along the red lines I've added here, not along the cyan lines in your example image.
Edited to add: For a method of finding the proper offset information to fill the hole and placing the image under the hole, see my other answer in this thread.
You can find the location of the cutout in your overlay image, then use that information to properly place your under image with a command like this...
convert overlay.png -background none \
\( +clone -alpha extract -trim \
-set option:offset +%[fx:page.x]+%[fx:page.y] +delete \) \
\( image.jpg -rotate -10.7 -set page %[offset] \) \
-set page %[fx:u.w]x%[fx:u.h] +swap -layers merge result.png
This makes use of the fact that the bounding box dimensions of the rotated input image are the same as the bounding box dimensions of the cutout of the transparent region in the overlay image.
That reads in the overlay, and inside parentheses it makes a clone of it, extracts the alpha channel, and trims the result to find the offset of the cutout. It saves the offset to a variable named "offset".
Then inside another set of parentheses it reads in the under image, rotates it the known -10.7 degrees, and uses that variable "offset" to set the paging offset on the rotated "image.jpg".
Then outside the parentheses it uses the width and height of the overlay to set the paging dimensions for the under image.
It finishes by swapping the order of the images to put the overlay on top, then merging the two layers to create the output.
Here is an alternate to GeeMack's excellent ImageMagick solution. This computes the center of the original input.jpg, and the center of the transparent region in the Overlay.png. Then it uses +distort SRT to translate and rotate the image before finally compositing with -layers merge.
convert Overlay.png \
\( +clone -alpha extract -trim -set option:center "%[fx:page.x+w/2],%[fx:page.y+h/2]" +delete \) \
\( Image.jpg -virtual-pixel none +distort SRT "%[fx:w/2],%[fx:h/2] 1 -10.7 %[center]" \) \
+swap -layers merge +repage result2.png
The second line is much line GeeMack's, but it computes the center of the transparent region's bounding box and saves that in the "center" argument and then deletes the trimmed image.
The third line computes the center of the Input.jpg image (before rotation). It then uses +distort SRT to translate from the input center, (scale=1) and rotate -10.7 and translate to the center of the transparent region's bounding box.
See https://imagemagick.org/Usage/distorts/#srt
I'm trying to execute the following set of transformations without knowing the absolute width or height of the target image:
1. Crop image A by 10px on every size :: A1
2. Create duplicate of A1 translating image by 1270px on the y-axis :: A2
3. Create montage of A1 && A2 :: A3
4. Translate A3 by 385px on the y-axis :: A4
5. Crop A4 at 100% width, and 1270px tall (box from 0,0 to WIDTH,1270) :: A5
My issue is how do I do steps 1 and 5 with relative coordinates? Below are my steps that I've come up with:
1. convert A.jpg -shave 10x10 A1.jpg
2. convert A1.jpg -page +0-1270 -background none -flatten A2.jpg
3. montage A1.jpg A2.jpg -geometry +0+0 A3.jpg
4. convert A3.jpg -page +0-385 -background none -flatten A4.jpg
5. convert A4.jpg ????? A5.jpg
Updated Answer
Ok, I think I understand what you want a bit better now. Here's how I would do it:
convert start.jpg -crop +0+383 +repage \
\( -clone 0 -crop x1270+0+0 \) \
\( -clone 0 -crop x1270+0+1270 \) \
-delete 0 +append result.jpg
The first line says..."Take the starting image and crop off the top 383 pixels and reset all the sizes to match what is left. Call that the first image from now onwards."
The second line says..."To one side (because of the parentheses), clone the first image and crop out the full width and 1270 pixels in height from the top. Hold onto that till later - i.e. keep it in the image list.".
The third line says..."To one side (because of the parentheses), clone the first image, and crop out a piece the full width and 1270 pixels in height, but start 1270 pixels from the top. Hold onto that till later - i.e. keep it in the image list."
The last line says..."Delete the initial image, and then take the two slices in the image list and append them side-by-side, Save as result.jpg".
Original Answer
I think we will need to work together on this one, but it can be done. Let's start with a concrete image that is a 400x250 gradient with a 15px black border:
convert -size 250x400 gradient:red-cyan -rotate 90 -bordercolor black -border 15 A.png
So, step 1.
convert A.png -shave 10x10 A1.png
Step 2&3. I don't get the point of these! You appear to be trying to add transparent space to a JPEG which doesn't support transparency. Also, I can't tell what you are montaging where. Please try and express what you want with these two steps in plain English, like "add a transparent area N pixels wide/tall above/below, left/right of A2", or maybe "add a transparent area such that the new dimensions are X,Y and the original A2 image is at the bottom-right of the new canvas."
If I have a stab at steps 2&3, I'll guess this (and add a purple border so you can see it on StackOverflow's white background). I am appending a transparent area 1270 pixels tall below the image.
convert A.png -background none -shave 10x10 xc:none[1x1270\!] -append b.png
Step 4&5. As above.
Or maybe you mean this:
convert A.png -background magenta -shave 10x10 -gravity southeast -extent 1270x385 result.png
I think we can get you down to a single command, with no intermediate files, if we understand your needs.
I have a PNG image with transparent areas, squares/rectangle areas that contains transparency.
I would like to know if there is some way that i can know the top,lef,width,height of theses transparent areas in the image.
Thanks for any help
Updated Answer
In the intervening years, I have come across a simpler solution, so I thought I would update it so anyone else seeing it can get the benefit of the latest and greatest.
Start off just the same, by extracting the alpha layer to an image of its own and invert it:
convert start.png -alpha extract -negate intermediate.png
Now perform a "Connected Component Analysis" on that:
convert start.png -alpha extract -negate \
-define connected-components:verbose=true \
-define connected-components:area-threshold=100 \
-connected-components 8 -auto-level result.png
Objects (id: bounding-box centroid area mean-color):
0: 256x256+0+0 128.7,130.4 62740 srgb(0,0,0)
3: 146x8+103+65 175.5,68.5 1168 srgb(255,255,255)
2: 9x93+29+42 33.0,88.0 837 srgb(255,255,255)
1: 113x7+4+21 60.0,24.0 791 srgb(255,255,255)
You will see there is a header line and 4 lines of output and each has a colour at the end, the first line is black, and corresponds to the entire shape, and the the last three are white, corresponding to the three transparent areas. It is basically the second field on each of the last three lines that you want. So, 146x8+103+65 means a box 146px wide by 103px tall offset 103px to the right of the top-left corner, and 65px down from the top-left corner.
If I draw those in, in red, you can see what it has identified:
convert result.png -stroke red -fill none -strokewidth 1 \
-draw "rectangle 103,65 249,73" \
-draw "rectangle 29,42 38,135" \
-draw "rectangle 4,21 117,28" result.png
Original Answer
The following may help you get to an answer but I have not developed it all the way through to completion - people often ask questions and then never log in again and there is quite a lot of effort involved...
Let's start with this input image - where the white areas are transparent:
You can extract the alpha channel from an image with ImageMagick like this:
convert input.png -alpha extract -negate alpha.png
which gives this, where white areas are transparent
Ok, one approach is to find the bounding box of the white areas, you can do this with trim and it will give you the bounding box that encloses the white areas:
convert input.png -alpha extract -format "%#" info:
245x114+4+21
So the bounding box is 245px wide and 114px high starting at offset +4+21 from top left. I can draw that on the image to show it:
So, that is a start.
Also, you can get ImageMagick to enumerate the pixels in text format, so you can run this command
convert input.png -alpha extract -negate txt: | more
# ImageMagick pixel enumeration: 256,256,255,gray
0,0: (0,0,0) #000000 gray(0)
1,0: (0,0,0) #000000 gray(0)
2,0: (0,0,0) #000000 gray(0)
which tells you that the image is 256x256 and that the first 3 pixels are all black. If you want the white ones (i.e. transparent ones) you can do this:
convert input.png -alpha extract -negate txt: | grep FFFFFF | more
4,21: (255,255,255) #FFFFFF gray(255)
5,21: (255,255,255) #FFFFFF gray(255)
6,21: (255,255,255) #FFFFFF gray(255)
7,21: (255,255,255) #FFFFFF gray(255)
This tells you that pixel 4,21 is the top left corner of your transparent area - I'm glad it matches the output from the bounding box method above :-)
So, you can easily get a list of all the pixels that are transparent. This approach could be developed, or something similar coded up in Ruby (RMagick) to find contiguous areas of black - but that is beyond the scope of this answer for the moment - as I am not a Ruby programmer :-)
Ok, I have learned some Ruby this afternoon and, no laughter please, this is my first Ruby program. It is probably pretty ugly and more like Perl or C (my preferred languages) but it works and finds the rectangular transparent areas.
#!/usr/bin/ruby
require 'RMagick'
include Magick
infile=ARGV[0]
img = ImageList.new(infile)
w=img.columns
h=img.rows
#Extract alpha channel into pixel array
px=img.export_pixels(0,0,w,h,"A")
for row in 0..h-1
for col in 0..w-1
thispx=px[w*row+col]
if thispx<32768 then
a=row
b=col
# Find extent (c) of rectangle towards right
for r in col..w-1
thispx=px[w*row+r]
if thispx<32768
c=r
else
break
end
end
# Find extent (d) of rectangle towards bottom
for s in row..h-1
thispx=px[w*s+col]
if thispx<32768
d=s
else
break
end
end
# Blank this rectangle as we have located it
for r in row..d
for s in col..c
px[w*r+s]=65535
end
end
# Tell caller about this rectangle
printf "%d,%d %d,%d\n",a,b,d,c
end
end
end
Run it like this:
bounds.rb input.png
I am creating a rounded rectangle mask using
convert -size 256x256 xc:none -draw "roundrectangle 0,0,256,256,47,47" mask.png
This works fine. However using the same command for 16x16 as follows
convert -size 16x16 xc:none -draw "roundrectangle 0,0,16,16,3,3" mask.png
produces a mask.png in which the rounded corners don't look correct. Infact top left corner looks ok and bottom right corner looks distorted.
My convert version is
Version: ImageMagick 6.8.9-6 Q16 i586 2014-09-06 http://www.imagemagick.org
For each image the rounded radius is 47/256 ~= 3/16 ~= 18%
Am I not running the commands correct or are these artifacts expected? Could this be imagemagick limitation.
My final aim is to use this mask and composite it to make an application icon for various sizes ranging from 16x16 all the way to 1024x1024. Since the mask is created wrong so are the final icons when compositing.
This is more related to a basic canvas overflow. Just remember that an array of pixels starts at 0 and ends at n-1 (where n is the size of the array.)
If you draw on an image with the size 16x16, the first pixel will have a access coordinate of 0,0 and a the last pixel at 15,15. This is the same with your first example, but the image & curve is large enough not to notice the last pixel is trimmed off.
convert -size 16x16 xc:none -draw "roundrectangle 0,0,15,15,3,3" mask.png