使用nginx+lua+ImageMagick实现自动缩略图

nginx_image_thumb.conf

server {
    listen   80;
    server_name pic.example.com;

    root /path_to/images;

    location / {
        index index.html;
    }
    
    location ~ (.*)!(t|c|tx)(\d+)(x(\d+))?.(gif|jpg|jpeg|png)$ {
        
        root /path_to/thumbs;

        set $image_root /path_to/images;
        set $thumb_root /path_to/thumbs;
        set $file "$thumb_root$uri";
        
        default_type 'image/jpeg';

        if (!-f $request_filename) {
            rewrite_by_lua '
                
                file_exists = function(name)
                   local f=io.open(name,"r")
                   if f~=nil then io.close(f) return true else return false end
                end

                get_path=function(str,sep)
                    sep=sep or "/";
                    return str:match("(.*"..sep..")");
                end
             
                local index = string.find(ngx.var.uri, "!");
                local originalUri = string.sub(ngx.var.uri, 0, index-1);
                local size = string.sub(ngx.var.uri, index+1);
                local mode = string.sub(size, 0, 1);
                index = string.find(size, "%.");
                size = string.sub(size, 2, index-1);

                if file_exists(ngx.var.image_root .. originalUri) then
                    local command =  "";
                    if mode == "t" then
                        command = "convert " .. ngx.var.image_root ..  originalUri  .. " -resize \'" .. size .. ">\' " .. ngx.var.file; 
                    elseif mode == "c" then 
                        command = "convert " .. ngx.var.image_root ..  originalUri  .. " -thumbnail " .. size .. "^ -gravity center -extent " .. size .. " " .. ngx.var.file;
                    end
                    os.execute("mkdir -p " .. get_path(ngx.var.file));
                    os.execute(command);
                    ngx.req.set_uri(ngx.var.uri, true);
                else
                    ngx.exit(404); 
                end
            ';
        }
        expires 30d;
    }

    location ~ .*\.(jpg|jpeg|gif|css|png|js|ico|swf|xml)$ {
        expires   30d;
    }
}