基于mini_magick多图片合并/添加水印

class ImageService

  require "mini_magick"

  def self.tmp_dir
    dir = "#{Rails.root}/tmp/image"
    FileUtils.mkdir(dir) unless File.exists?(dir)
    dir
  end

  def self.composite(image_paths)
    to_path = "#{tmp_dir}/composite_#{SecureRandom.uuid.to_s.strip}.jpeg"
    montage_commond = image_paths + ["-strip", "-quality", "70", "-tile", "1x#{image_paths.length}", "-geometry", "+0+0", to_path]
    MiniMagick::Tool::Montage.new{|m| m.merge! montage_commond}
    to_path
  end

  def self.compress(image_path, watermark = false)
    to_path = "#{tmp_dir}/compress_#{SecureRandom.uuid.to_s.strip}.jpeg"
    image = MiniMagick::Image.open image_path
    image.combine_options do |b|
      b.strip
      b.quality "60"
    end
    if watermark
      watermark_image = MiniMagick::Image.open("#{Rails.root}/app/assets/images/special_watermark.png")
      watermark_width = (image.width * 0.9).to_i
      watermark_height = (watermark_image.height * (watermark_width / watermark_image.width.to_f)).to_i
      watermark_image.resize "#{watermark_width}x#{watermark_height}"
      image = image.composite(watermark_image) do |c|
        c.gravity 'center'
      end
    end
    image.write to_path
    to_path
  end
end

图片合并

image_paths = files.map{|f| f.tempfile.path}
composite_path = ImageService.composite(image_paths)

File.open(composite_path) do |f|
    attachment.path = f
end

文件格式大小限制

def create_company_change
    files = params[:file_path]
    flag, flash[:msg] = check_file(files)
    unless flag
      redirect_to my_whmall_account_informations_url and return 
    else
      #todo
   end
end
def check_file(files)
    max_size = 1024 * 1024 * 3 #3M
    file_type = ['image/gif ', 'image/png', 'image/jpeg', 'application/pdf']
    return false, '上传文件不能为空' if files.blank?
    files.each do |file|
       return false, '文件不能大于3M' if file.size > max_size
       return false, '可上传的图片格式将限于jpg、gif、png和pdf' unless file_type.include? file.content_type
    end
    return true, '变更申请提交成功,请等待审核。'
  end