Legacy ImageMagick Discussions Archive

@snibgo: so does that mean a channel separation is just taking one value and then using the same value for all three channels?

I post it back to the canvas and then save it as a png:

Oh ok, so my function is this

for (var i = 0; i < data.length; i += 4) {
var grayscale = data[i]*0.2126 + data[i +1]*0.7152 + data[i +2]*0.0722;
data[i] = grayscale; // red
data[i + 1] = grayscale; // green
data[i + 2] = grayscale; // blue
}

so when I leave the green and blue out

for (var ...

Thank you so much for taking the time to explain. It's not so much the problem of IM, I am trying to rebuild it with Javascript but everytime when I do I end up with something that looks like this https://www.dropbox.com/sh/yoqcjwlp6soefgy/AACuTGeM65eKW5RmpxAMLpaQa?dl=0

I want it to be like in the ...

Ok, but I still don't understand how IM7 does that. I am trying to build a JS code that grayscales it and then takes one channel of the image just like here:

https://en.wikipedia.org/wiki/Grayscale#Grayscale_as_single_channels_of_multichannel_color_images

the problem that I have is everytime when ...

Is there a difference in the file size then? It should be, the file in IM7 should be smaller, no?

Ok, so IM6 doesn't use this forumula R*0.2126 + G*0.7152 + B*0.0722 ?


But how does that work with only one single grayscale channel? Will white still be white then?

Hi,

I am trying to understand what happens when I use this command convert rose: -channel R -separate separate_red.gif found here http://www.imagemagick.org/Usage/color_basics/#channels ?

As far as I understand it separates one channel which means the other two are set to 0 and then grayscales ...

perfect thank you!

Oh hold on, since RGB is all the same it means it is greyscale right?

it says

Format: PNG (Portable Network Graphics)
Class: DirectClass
Geometry: 718x256+0+0
Resolution: 72x72
Print size: 9.97222x3.55556
Units: Undefined
Type: TrueColorAlpha
Endianess: Undefined
Colorspace: sRGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
alpha: 8 ...

Hi,

Not sure if this is the right forum here, and I'm a noob, sorry! How do I check if a picture is a perfect grayscale?

I tried identify -verbose myfile.png

and got these numbers:

Rendering intent: Perceptual
Gamma: 0.454545
Chromaticity:
red primary: (0.64,0.33)
green primary: (0.3,0 ...

I got it !

I think you were right, it has to be 'grayscalematte' instead of 'grayscale'

Hi,

Thanks! My python code is like this:

def grey():
with Image (filename="image7.png") as img:
img.type='grayscale';
img.save(filename="image7_grey.png")

When I do identify I get this:

Image: image7.png
Format: PNG (Portable Network Graphics)
Class: DirectClass
Geometry: 799x168+0+0 ...

Hi,

I am trying to save a PNG. My version is imageMagick 6.7.7.10

I am using it with python in ubuntu and right now I am just changing the saturation via img.modulate(saturation=0.0)

I found somewhere that I could use:

img.alpha = True
# or
img.background_color = Color('transparent')

However ...