how do sizing image with paperclip gem - ruby-on-rails

Question

i want to use avatar through paperclip. in tutorial use gravatar
messages_helper.rb
def recipients_options(chosen_recipient = nil)
s = ''
User.all.each do |user|
s << "<option value='#{user.id}'
data-img-src='#{gravatar_image_url(user.email, size: 50)}'
#{'selected' if user == chosen_recipient}>
#{user.name}</option>"
end
s.html_safe
end
i change on this code and it working.
module MessagesHelper
def recipients_options(chosen_recipient = nil)
s = ''
User.all.each do |user|
s << "<option value='#{user.id}' data-img-src='#{user.avatar.url(:thumb)}'
#{'selected' if user == chosen_recipient}>#{user.username}</option>"
end
s.html_safe
end
end
new.html.erb
<div class="form-group">
<%= label_tag 'recipients', 'Choose recipients' %>
<%= select_tag 'recipients', recipients_options(#chosen_recipient), multiple: true, class: 'form-control chosen-it ' %>
</div>
user.rb
has_attached_file :avatar, :styles => { :medium => "150x150>", :thumb => "30x30#" }, default_url: "https://s3.amazonaws.com/myinstick/logo/instagram-icon.png"
validates_attachment_content_type :avatar, :content_type => /\Aimage\/.*\Z/
But! if user dont have avatar, that use image paperclip default. and it does not scaling and It looks big. how to set the style or size.
it looks like this

Answer 1

in your model:
has_attached_file :avatar,
:styles => { thumb: "100x100#", medium: "300x300#", large: "900x500#"}
or whatever size you want it to be. The # is for cropping. It will select the center of the image and crop the specified height and width from there. You can also just use the default > if you don't want the cropping... and in your view:
<%= image_tag #user.avatar.url(:medium) %>

Answer 2

I solved the problem. Drop-down list uses
jquery.image-select.js
(function($) {
// Image template, this can be overridden from the constructor (options.template),
// must contains {src} placeholder. Ther eare two class names 'chose-image' or 'chose-image-small', modifiy in CSS
var fn_template = '<img class="{class_name} " src="{url}" />';
// Store the original 'chosen' method
var fn_chosen = $.fn.chosen;........
I can set class for all images, like this
var fn_template = '<img class="{class_name} image-circle-minisize" src="{url}" />';
and everything works