Transparent Image Using Rmagick

Ruby
1

Hello,

I use rmagick to create a new image.
How can I make this image with 50% transparency?

Thanks

2

I use rmagick to create a new image.
How can I make this image with 50% transparency?

Take a look at the tutorials on the rmagick website (
http://rmagick.rubyforge.org/ ). This one features transparency/opacity
:

http://rmagick.rubyforge.org/Polaroid/polaroid.html

I don’t use rmagick very much, but I found these by googling “rmagick
transparent”.

Hope this helps,

Chris

3

I found here an example:
http://blog.corunet.com/english/the-definitive-heatmap
it works, but it use external ImageMagick convert program

@opacity = “0.50”
@path = ‘./’
transparency = "convert “<<@path<<‘image.png -channel A -fx
"A*’<<@opacity<<'” '<<@path<<‘image_transparent.png’
system(transparency)

How can I transform this in ruby rmagick code?

Chris L. wrote:

I use rmagick to create a new image.
How can I make this image with 50% transparency?

Take a look at the tutorials on the rmagick website (
http://rmagick.rubyforge.org/ ). This one features transparency/opacity
:

http://rmagick.rubyforge.org/Polaroid/polaroid.html

I don’t use rmagick very much, but I found these by googling “rmagick
transparent”.

Hope this helps,

Chris

4

Radu C. wrote:

Hello,

I use rmagick to create a new image.
How can I make this image with 50% transparency?

Thanks

If you just want a solid-color image that’s 50% transparent, specify the
color and transparency when you create the image:

img = Magick::Image.new(columns. rows) {self.background_color =
Magick::Pixel.new(rr, gg, bb, Magick::MaxRGB/2)}

where columns and rows specify the size of the image, and rr, gg, bb
specify the red, green, and blue channels.

If you have an image already and you want to change the opacity, use the
#opacity attribute:

img.opacity = Magick::MaxRGB / 2

http://www.simplesystems.org/RMagick/doc/imageattrs.html#opacity
http://www.simplesystems.org/RMagick/doc/struct.html#Pixel
http://www.simplesystems.org/RMagick/doc/image1.html#new

5

On Jul 26, 8:07 am, Radu C. [email protected] wrote:

What makes you think it doesn’t work? How are you viewing the image?
What kind of image is it? A GIF? A JPEG?

6

Thanks Tim for your reply.

My image is not with one solid color.
I have already an image to change the opacity.

Unfortunately, I tried
img.opacity = Magick::MaxRGB / 2
but it doesn’t working

I tried also with background_color = ‘none’.

Any clues?

Thanks

Tim H. wrote:

Radu C. wrote:

Hello,

I use rmagick to create a new image.
How can I make this image with 50% transparency?

Thanks

If you just want a solid-color image that’s 50% transparent, specify the
color and transparency when you create the image:

img = Magick::Image.new(columns. rows) {self.background_color =
Magick::Pixel.new(rr, gg, bb, Magick::MaxRGB/2)}

where columns and rows specify the size of the image, and rr, gg, bb
specify the red, green, and blue channels.

If you have an image already and you want to change the opacity, use the
#opacity attribute:

img.opacity = Magick::MaxRGB / 2

RMagick 1.15.0: class Image (attribute methods)
RMagick 1.15.0: Miscellaneous classes
RMagick 1.15.0: class Image (class and instance methods, part 1)

7

On Jul 26, 8:43 am, Radu C. [email protected] wrote:

–
Posted viahttp://www.ruby-forum.com/.

Send the image and a script that reproduces the problem to rmagick AT
rubyforge DOT org and I’ll take a look at it.

8

Tim H. wrote:

On Jul 26, 8:07 am, Radu C. [email protected] wrote:

What makes you think it doesn’t work? How are you viewing the image?
What kind of image is it? A GIF? A JPEG?

It’s a png image.
The image generated with convert has opacity 50% (i viewed with acdsee)
The image generated with rmagick doesn’t have opacity.

9

Tim H. wrote:

On Jul 26, 8:43 am, Radu C. [email protected] wrote:

–
Posted viahttp://www.ruby-forum.com/.

Send the image and a script that reproduces the problem to rmagick AT
rubyforge DOT org and I’ll take a look at it.

Here is an example of script:

require 'RMagick'
image = Magick::Image.read('public/images/rails.png').first
image.opacity = Magick::MaxRGB / 2
image.write("public/images/rails_with_transparency.png")

(rails.png is the default rails logo from a new rails app)
theoretically, this should be working, but is not working,
the new image rails_with_transparency.png is the same as rails.png

10

Radu C. wrote:

I didn’t get any mail from you. Without the image I can’t help you.