I have more PNG images (let's say img1.png, img2_transparent.png, img3.png) and I want them flatten to one image.
Before I flatten them I set (I want second image was slightly transparent):
convert img2_transparent.png -alpha on -channel a -evaluate set 90%
Then I flatten them (order is img1.png, img2_transparent.png, img3.png):
convert *.png -flatten out.png
Result is ok, second "layer" has opacity 90%, BUT whole picture (thus all "three" layers) is "lightened". Colors are not so deep as I don't set alpha to img2_transparent.png.
How can I avoid this?
Thank you
If you want the images to show up in equal measure in the resulting image, the general formula is to set the opacity of each layer to
1/(1 + number of layers underneath)
where the base layer is at full opacity. The second image is then at opacity 1/2, the third image at opacity 1/3, the fourth image is at opacity 1/4.
convert base.png \
\( layer2.png -channel A -fx '0.5' \) \
\( layer3.png -channel A -fx '0.333' \) \
\( layer4.png -channel A -fx '0.25' \) ....
There is a well explained tutorial on Cambridge in Colour website. Scroll down to AVERAGING IMAGES IN PHOTOSHOP USING LAYERS.
Related
I want to generate an image out of 3 images. One of these images is the background, one the shape mask and one the color of the shape.
Here are the images:
shape.png
(transparent background, white circle in the middle and black circle inside and gray circle inside the black one)
shapecolor.png
background.png
The background.png should be the overall background. On top of that is the shape and all white parts (and also the white in the gray parts) should be in the color of shapecolor.png
I used simple mono color images to make it easier but I use some textures in reality ^^
I have no idea how to solve this problem in Imagemagick, the tool is very powerful and the documentation is not so easy to understand. Tried to solve this for 3h, but did not get the result, which should look like this:
Can anyone help please?
Here is one way to do it in Imagemagick. In the second line, extract the alpha channel from omg.png and save it in an mpr: in-memory image and then delete the clone. Then I use the mpr: image later in the last step.
convert red.png img.png \
\( +clone -alpha extract -write mpr:alpha +delete \) \
-compose multiply -composite \
green.png +swap mpr:alpha -compose over -composite \
result.png
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
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
Given a RGB image :
Given a grey scale, opacity 0% to opacity 100% black image:
How to add the alpha shadows upon the RGB image using a shell command ? (preferemce for ImageMagick Convert)
I would compose the images using the Multiply operator. The command
convert src.png overlay.png -compose Multiply -geometry 948x630 -composite out.png
produces:
I believe the example "Using Masks with Images" covers this. Simply disable the alpha channel, and copy over the second image as opacity composite. Add -negate option to invert the 0% ~ 100% opacity -- if needed.
convert map_image.png elevation_mask.png \
-alpha Off -compose CopyOpacity -composite \
out.png
I need to create an image to be used as a rollover background image. It's a circular pattern that is split into 8 pieces. Here's a screengrab of the main image (png with transparency):
And here's a screengrab of the mask image. It's the same size as the main image and features 'pie' pieces in order to mask all but the sector that is being hovered over.
I'm including screengrabs, as I believe the answer should be pretty simple (aren't all answers simple when you know them?!) so I'll save bandwidth, but I can upload the original files if it's helpful.
Here's the command I'm using to create the new masked image:
convert main.png \( mask.png -colorspace gray -alpha off \) \
-compose copy-opacity -composite new.png
The trouble is that the new image created has flattened the original image's alpha to a black background:
How do I get Imagemagick to preserve the original png's transparency?
You want masked composition to do this. http://imagemagick.org/Usage/compose/#mask
The technique is to compose the original image (the src) onto a fully transparent image of the same size (the dst), using a mask to limit composition area (the mask). It is a special case of the -composite operator, and involves 3 images, rather than 2 like the rest of the compose methods. You don't specify any -compose mode for this.
A quick way to get the fully transparent dst that you need for this technique is to clone the src image and zero out its alpha channel, then swap the order of src and dst so that they are in the right order for the -composite operation to follow:
convert main.png -alpha on \( +clone -channel a -fx 0 \) +swap mask.png -composite out.png
I was not satisfied with retroj's solution as it seems to ignore the grayscale of the mask.
This one worked for me:
composite -compose Dst_In \( mask.png -alpha copy \) main.png -alpha Set PNG32:result.png
or
convert -compose Dst_In \( mask.png -alpha copy \) main.png -alpha Set -composite PNG32:result.png
Dst_In method multiplies the alpha channels of two images. The trick here is to convert the grayscale mask to an alpha channel for it which is done with -alpha copy.