I have an image with some opaque white pixels (rgba = FFFFFFFF). I want to change those pixels to a different color with a different transparency, say rgba = 33333355.
I use
convert test.png -fuzz 1% -alpha set -fill '#33333355' -opaque '#ffffffff' test2.png
The pixel's colors are changed properly, but not the alpha values, so I get new pixels with rgba = 333333FF !
Why can I change the rgb value, but not the alpha value?? How can I change the alpha value also?
Thanks
Your just missing the -channel option. I believe the default channel value is 'RGBK,sync'; however, your attempting to alter pixels as 'RGBA'.
convert test.png \
-fuzz 1% \
-alpha set \
-channel RGBA \
-fill '#33333355' \
-opaque '#ffffffff' \
test2.png
Related
I have the following bar chart:
I transformed it to greyscale using the following command:
convert image.tif -set colorspace Gray -separate -average image_greyscale.tif
and my result was
It is greyscale indeed, but the axes and the legend are grey as well. This is obvious now, but I'd like them to be black, like in the original image. Something like this:
How can I do it? Remake the bar charts again, with a greyscale palette, is not possible right now.
I think what you want to do in ImageMagick is simpler than your command. Just do
Input:
convert barchart.png -colorspace gray result.png
Result:
You can select the plum colour and change that to gray20 and then select the lime colour and change it to gray80 like this:
magick chart.png -fuzz 10% \
-fill gray20 -opaque "rgb(68,1,84)" \
-fill gray80 -opaque "rgb(122,209,81)" result.png
Or, as a one-liner:
magick chart.png -fuzz 10% -fill gray20 -opaque "rgb(68,1,84)" -fill gray80 -opaque "rgb(122,209,81)" result.png
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.
I want to change all colors #FF00FF in an image to #0000FF while keeping shades, ideally. So I figured I should at least get it to change colors to begin with to see if the software is even capable of doing things like that.
However its only changing a bit of the color to white and only with a high Fuzz. So it's obvious that RGB in Imagemagick doesn't work like it does anywhere else and I can't find anything to explain how it works.
It seems to replace some off-white with pure white.
Using PHP I do:
exec("convert ".$dir."".$file." -channel RGB -fuzz 30% -opaque rgb\(255,0,255\) -fill rgb\(0,0,255\) ".$dir."".$file);
I am not 100% certain what you mean as you haven't provided a sample of what other software does, but I'll have a try and see if we can get there.
So, if we make a starting image, including your presumed shades of magenta on the left and some test colours on the right:
convert -size 256x256 gradient:black-magenta -size 50x256 \
xc:black xc:white xc:red xc:lime xc:blue +append start.png
And, you want to change magenta shades into blue. I would call that a hue modulation, so I would want to find out the hue angle between blue and magenta, so I would create a 2x1 image with one magenta and one blue pixel and get their HSI values:
convert xc:magenta xc:blue -append -colorspace hsi txt:
Output
# ImageMagick pixel enumeration: 1,2,65535,hsi
0,0: (54612.5,65535,43690) #D555FFFFAAAA hsi(300,100%,66.6667%)
0,1: (43690,65535,21845) #AAAAFFFF5555 hsi(240,100%,33.3333%)
And I can see their hues are 60 degrees apart (300-240). So I would use the -modulate operator, which takes a Brightness, Saturation and Hue, leave the first two unchanged at 100%, and modify the Hue by 60 degrees:
convert start.png -modulate 100,100,60 result.png
Or maybe that is not what you mean? Maybe you only mean to affect specific colour. If so, it gets harder... but not that hard :-)
First, extract the Hue, Saturation and Brightness layers to separate files:
convert start.png -colorspace HSL -separate -colorspace gray HSL-%d.png
That will give us the Hue as a single channel greyscale image in HSL-0.png, the Saturation in HSL-1.png and the Lightness in HSL-2.png.
Now we want to make a new LUT (Lookup Table) for the Hue channel, so we make a 360 pixel long LUT that maps 1:1, i.e. everything maps to normal.
convert -size 1x360 gradient: -rotate 90 greyscale.png
Then we want to dink with the lookups around magenta (300) and make them blue (240). So we want to subtract 60 degrees (which is 0.16 if you scale 0-360 degrees onto the range 0-1) from all pixels in the range 280-320 so there is some tolerance:
convert -size 1x360 gradient: -rotate 90 -colorspace gray -fx "i<280||i>320?u:u-0.16" hueCLUT.png
Now apply that LUT to the Hue of the original image and rebuild it...
convert HSL-0.png -colorspace gray hueCLUT.png -clut HSL-1.png HSL-2.png -set colorspace HSL -combine -colorspace RGB result.png
So, as a simpler script, that might become:
#!/bin/bash
# Make a hue CLUT, transforming magenta hues to blue
convert -size 1x360 gradient: -rotate 90 -colorspace gray -fx "i<295||i>305?u:u-0.16" -resize 256x1! hueclut.png
# Apply to the hue channel
convert start.png -colorspace HSL -write MPR:HSL \
-channel R -separate hueclut.png -clut \
\( MPR:HSL -channel G -separate \) \
\( MPR:HSL -channel B -separate \) \
-set colorspace HSL -combine -colorspace RGB 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
I had been searching for good algorithm for green screen chroma key using ImageMagick, but no satisfactory answer so far.
I would like to explore a simple method of using range selection along the HSV/HSB color space (similar to -fuzz) to select the green color I want and make them transparent. The -fuzz seems to apply only in RGB space, which is not desired.
Can anyone teach me how to select color with seperate range for H, S, V component, for example, 115-125 degree Hue, 40%-60% Saturation and 30-80% Value.
If there is other better chroma-key algorithm, your advice is highly appreciated too.
Thanks in advance.
Imagemagick's FX can be used to generate a alpha channel. The hue, saturation, lightness, & luma keywords exists, but you'll need to calculate the color value by max(r, g, b).
hueMin=115/360;
hueMax=125/360;
saturationMin=0.40;
saturationMax=0.60;
valueMin=0.30;
valueMax=0.80;
value = max( r, max( g, b ) );
(
( hue > hueMin && hue < hueMax ) && (
( saturation > saturationMin && saturation < saturationMax ) ||
( value > valueMin && value < valueMax ))) ? 0.0 : 1.0
Saving the above into a file named hsl-greenscreen.fx and execute it against an image with:
convert source.png -channel alpha -fx #hsl-greenscreen.fx out.png
The FX script will probably need additional tweaking to match expected results. You'll also notice this will take a bit of CPU to complete, but that can be improved on.
Another option would be to apply the same -fuzz options, but on each HSV channel. Simply split & clone each channel, apply -fuzz against a target grey, and compose an image mask.
convert source.png -colorspace HSV -separate +channel \
\( -clone 0 -background none -fuzz 5% +transparent grey32 \) \
\( -clone 1 -background none -fuzz 10% -transparent grey50 \) \
\( -clone 2 -background none -fuzz 20% -transparent grey60 \) \
-delete 0,1,2 -alpha extract -compose Multiply -composite \
-negate mask.png
Then assign the mask as the images alpha channel
convert source.png mask.png -alpha Off -compose CopyOpacity -composite out.png