I have an icon with a fully transparent background and a semi-transparent, white foreground. I would like to make the foreground fully opaque, can this be achieved with ImageMagick?
I have tried juggling different combinations of these;
http://www.imagemagick.org/discourse-server/viewtopic.php?t=12619
http://www.imagemagick.org/discourse-server/viewtopic.php?t=18196
http://www.imagemagick.org/discourse-server/viewtopic.php?t=16718
, but cannot produce the desired result. Any tips?
It would be easier if you posted your icon, but my testing shows that this works for what I think you have:
convert icon.png -channel A -threshold 75% output.png
The above is somewhat coarse as it makes all partially transparent pixels fully opaque. If you wanted to be a bit more surgical, you could only set the opacity to fully opaque when the Red, Green and Blue pixels are greater than 90% and the original opacity (alpha) is between 40%-60% like this:
convert icon.png -channel A \
-fx "(r>0.9 && g>0.9 && b>0.9 && a>0.4 && a<0.6) ? 1.0 : a" output.png
Related
Since it is hard to me to explain what I'm trying to do, I'm gonna show you this page to show you what I'm trying to reproduce and understand:
https://optifine.net/showCape?colTop=FF0000&colBottom=00FF00&colText=0000FF&colShadow=FD0000
which outputs this:
and this one https://optifine.net/showCape?colTop=FF00FF&colBottom=0034EE&colText=000000&colShadow=FF00E2 outputs this:
You can modify the hexadecimal colors, basically I'm trying to reproduce something like that. Basically you modify the colors and it gives you an image at the end with the colors you used.
I've tried to make the "possible" template that could be used on the page on Photoshop which can be downloaded here, it is a .psd file, that's because of the Alpha Channel, which I'm not even sure if done correctly. But based of these RGBA channels it should be possible to change the color. Can be downloaded here: https://workupload.com/file/4xYkgQMk
So what I know so far is that there is a template with RGBA channel. Each channel is indepedent so it apperantly doesn't matter if it's RGBA and at the end R channel is used to turn into another color other than red, where I'm not sure about that.
I've asked the developer he told me that these channels get interpolated with the real color after that, probably the one you choose.
Basically what is happening at showCape? and its URL parameters is that, lets assume colTop got assigned to the red channel then when you put a color in colTop it will get a fixed color that it will encode or something.
So the template has 4 Channels RGBA that can be made in Photoshop, the white color 255,255,255 means basically full and the black 0,0,0 means complete black. Like that you can setup brightness scales for the template.
I just don't know how to modify the channels and I don't understand how to use the Alpha channels properly or set them up.
I'm also not sure in which programming languages it is possible to peform and if you can test the template directly in something like Photoshop. Is it possible to do it in JavaScript or something to easy setup and if not on what then, to test it fast?
Ok, so here's how you can generate that sort of thing with ImageMagick, which is included in most Linux distros and is available for macOS and Windows. Note that there are Python, PHP, node.js and other bindings available.
First, generate a red rectangle:
magick -size 200x150 xc:red red.png
Now see how to do the same thing with hex codes:
magick -size 200x150 xc:"#ff0000" red.png
Now, draw a red rectangle with a blue one on top:
magick -size 200x150 xc:red -fill blue -draw "rectangle 10,10 80,140" redandblue.png
Now make the blue transparent:
magick -size 200x150 xc:red -fill blue -draw "rectangle 10,10 80,140" -transparent blue redandtrans.png
Now make a gradient from lime green to magenta:
magick -size 200x150 gradient:lime-magenta gradient.png
Now overlay the red rectangle with transparent window onto the gradient:
magick gradient.png redandtrans.png -composite overlay.png
Now add text:
magick overlay.png -fill "#0000ff" -pointsize 16 -draw "text 90,40 'Coloured text'" result.png
And now do the whole thing again, in one go:
magick -size 200x150 gradient:lime-magenta \
\( xc:red -fill blue -draw "rectangle 10,10 80,140" -transparent blue \) \
-composite \
-fill "#0000ff" -pointsize 16 -draw "text 90,40 'Coloured text'" result.png
Now you have provided a template, I can separate out the channels with ImageMagick like this and append them side-by-side with Red channel on the left, then Green, then Blue then the alpha/transparency channel on the right. I also added a red box around each one so you can see the extent on StackOverflow's white background.
magick template.png -separate -scale 100x +append channels.png
Keywords: ImageMagick, absolute basics, tutorial, transparency, compose, overlay, command line, image processing.
this sounds like indexed colors / palette effect from the VGA days (like plasma, water and fire) Where you change the palette (in a specific way) and image changes with it.
The idea is that Your image/sprite does not contain RGB colors directly but color indexes from palette instead. Where part of the palette for your image/sprite contains a color gradient so gradients on image are also gradients on index (neighboring shades have also neighboring indexes). Many old pixelart sprites and images from the old days are done this way (sorted palette).
Now you can simply chose few colors in that part of palette and interpolate the rest of the gradient (linearly or better).
To mimic this your need:
have a indexed color pixel art with sorted palette
For example You can convert your image into BMP or GIF with palette and sort the colors.
detect the part of palette with color gradient
change/update the gradient
re-render or recolor image.
I'm trying to make a capcha solver, but I have ran into some trouble. The captcha that I am trying to solve has different coloured backgrounds.
I need to convert it to black text on white background so that it could easily be recognised by tesseract-ocr
I have tried
convert *.png -threshold 50% *.png which only shows some of the digits.
The problem with simple 50% thresholding is that both colours may be lighter than 50% grey and will therefore come out as white. Or, conversely, both colours may be darker than mid-grey and therefore bith come out as black.
You need to do a 2-colour quantisation to get just 2 colours, then go to greyscale and normalize so the lighter colour goes white and the darker one goes black. I am not near a computer, to test, but that should be:
convert input.png -colors 2 -colorspace gray -normalize result.png
Now, you will find some images are inverted (black on white instead of white on black), so you can either test the top left corner pixel and if it is white, then invert the image. Or, you could get the mean of the image and if it is more than 0.5 that would indicate that the image is largely white and therefore needs inverting.
Invert with:
convert input.png -negate output.png
Get top-left pixel with:
convert image.png -format '%[pixel:p{0,0}]' info:-
Get mean value with:
convert image.png -format "%[mean]" info:-
I'm trying to overlay a green image over another image, and then convert the green color to transparent. The code I use is below. It works okay, however it leaves a slight green border. What's the best way to have this green border not show up? I tried using fuzz, however results with this vary. Sometimes it cuts out other colors. Is there a better way to prevent the green border than using fuzz?
convert image.png ../greenoverlay.png -layers merge image.png;
convert image.png -fuzz 41% -transparent \#00FF00 final.png;
Thank you all!
I've lots of images with a white background and I need to remove it (make it transparent). I've already tried imagemagick convert and for some image that worked quite well, but still cannot be used on dark background.
I'm kind a noob in this branch of programming... Someone know some good algorithms to remove the background?
Plus, would be great if it could correctly process an image like this:
http://dev.addvert.it/cache/24eeab00e5987452d09fbeec0c7678d6_w472_h472_sc.jpg
The problem with convert diff is it erase a lot of the image, while the border algo doesn't touch the central part.
I totally understand how hard is for a calculator to do something like this and I'm pretty amazed with the results of convert, but if there's the chance of a better solution, why not ask? :D
You are not constrained to converting white pixels to transparent. You could maybe take the colour of the top-left corner pixel and make all pixels that colour transparent and it will work for black backgrounds too:
As suggested by #emcconville, the first of the following two options is more succinct:
convert towel.jpg -fill none -fuzz 2% -draw 'matte 0,0 replace' output.png
or, per my original,
convert towel.jpg -alpha on -fill none -fuzz 5% -draw 'color 0,0 replace' output.png
You may find this more readable...
convert towel.jpg -fuzz 5% \
-transparent $(convert towel.jpg -format "%[pixel:p{0,0}]" info:) \
output.png
In the second line, $(convert ...) just gets the colour of the top-left pixel and feeds that into the middle of the outer convert command as the colour to make transparent - but it is only doing the same thing as the first version.
I have a grey scale image, from which I wish to convert all grey pixels into half transparent pixels, and white ones into transparent pixels.
How could I process a grey scale raster image via shell ?
Input :
Output (here made via Gimp):
Current Gimp process via GUI:
GIMP 2.6 > Load your shaded relief image (....shaded.tif : are grayscale)
or a screenshoot of your shaded relief (screenshot : RGB colors)
Force it to be RGB: Gimp > Image > Mode > RGB, click.
Delete the grey : Colors > "color to alpha" pop up > uncheck "preview", click on the horizontal color rectangle > "Color to alpha color picker" pop up> bottom right corner, click on the icon eyes dropper > choice you color of to delete (some grey pixel in a flat plain) > validate.
Delete an other color (white, black background) > same.
File > save as > ProjectName_relief_whitened.png (to keep transparency)
[note: SO images display, and image background CSS makes hard to see the subtile differences between files.]
Given the following gray scale input.png :
1a. To make black pixels of this image transparent and linearly keep the white pixels as they are, run this command:
convert source.png -alpha copy -fx '#fff' result.png
1b. To make white pixels transparent and linearly keep the black as they are, use:
convert source.png -alpha copy -channel alpha -negate +channel result.png
Manual:
convert – is the ImageMagic command (one of several)
source.png – is the greyscale source image.
-alpha copy – it copy contents of the previous file into the alpha channel.
-channel alpha – it specify that following operators only should affect the alpha channel.
-negate – it invert the current channel (channel alpha).
+channel – Specify that following operators only affect the opposite channel. For us, it switch focus from the alpha channel, to the color channel. (color channel is initially the default)
-fx '#000' – Replace current channel (for us, the color channel) contents with black pixels, so the end result actually fully depends on the alpha channel. If not included, all semi-transparent pixels in generated image will retain colors, from #FFF (white) to #000 (black).
Result of 1b:
Wiping out plains:
An additional processing could wipe out most of the flat plains, which appears around greys (#DDDDDD) with opacity:~50%. This could be done by :
convert input.png -fuzz 8% -transparent "#DDDDDD" grey_no.8pc.png
convert grey_no.8pc.png -alpha copy -channel alpha -negate +channel result.grey_no.png
so the plains avoid an useless #DDDDDD, opacity:50% overlay.
See also:
ImageMagick options: http://www.imagemagick.org/script/command-line-options.php