一个简单的QQ隐藏图生成算法
隐藏图不是什么新鲜的东西，具体表现在大部分社交软件中，预览图看到的是一张图，而点开后看到的又是另一张图。虽然很早就看到过这类图片，但是一直没有仔细研究过它的原理，今天思考了一下，发现挺有趣的，所以自己也写了个简单的算法把两张图片合成为一张隐藏图。
比如下面这张图。
当背景颜色为白色时，通常也就是在预览状态下，它是这个样子的
而当背景颜色变黑以后，通常也就是点开图片以后，它是这样子的。。
隐藏图原理
我们知道一张图片中具有透明度的像素会叠加一部分的背景色，因此当背景色为白色时，所有具有透明度的白色像素全部显示为纯白色，而当背景色为黑色时，所有具有透明度的黑色会显示为纯黑色。因此我们只需要把图片一的所有像素根据其灰度值转换成不同透明度的黑色，将图片二的所有像素根据其灰度值转换成不同透明度的白色，并将两图的所有像素按照任意规律交叉排列，即可生成隐藏图。这样当背景色为黑色时，图一的所有像素将会显示为纯黑色，图二的所有像素会因为其透明度不同显现出不同的灰色，此时图一隐藏，图二显现，反之同理。
算法实现
基本的算法思路上面已经提过了，可以说是一个相当简单的算法了。不过具体有几点需要注意：
- 由其原理可知，隐藏图只能是黑白的，不能是彩色的，因此当遇到彩色像素时，需要将其转换成灰度。对于彩色转灰度，心理学中有一个公式：Gray = R*0.299 + G*0.587 + B*0.114，我们需要做的是根据算出来的灰度设定像素透明度。在白色背景下，黑色像素的灰度会随着像透明度增高而降低，在黑色背景下，白色像素的灰度会随着透明度增高而增高。
- 考虑到需要合成的两张图片尺寸不一致，为了保证生成的隐藏图能够完成保留两张图片信息并且不发生变形，我们需要将最终图片的长和宽设定为两张图片尺寸中最大的长和最大的宽。
好的，接下来把我的代码实现贴出来吧
1 using System;
2 using System.IO;
3 using System.Drawing;
4
5 class MainClass
6 {
7 public static void Main(string[] args)
8 {
9 //图片一的文件路径
10 Stream blackImageReader = new FileStream("/Users/shiyidu/Desktop//1.jpg", FileMode.Open);
11 Bitmap blackImage = new Bitmap(blackImageReader);
12
13 //图片二的文件路径
14 Stream whiteImageReader = new FileStream("/Users/shiyidu/Desktop//2.jpg", FileMode.Open);
15 Bitmap whiteImage = new Bitmap(whiteImageReader);
16
17 //生成最终图片
18 Bitmap finalImage = CalculateHiddenImage(blackImage, whiteImage);
19
20 //最终图片保存路径
21 Stream imageCreater = new FileStream("/Users/shiyidu/Desktop//final.png", FileMode.Create);
22 finalImage.Save(imageCreater, System.Drawing.Imaging.ImageFormat.Png);
23 }
24
25 private static Bitmap CalculateHiddenImage(Bitmap blackImage, Bitmap whiteImage)
26 {
27 int b_width = blackImage.Width;
28 int b_height = blackImage.Height;
29 int w_width = whiteImage.Width;
30 int w_height = whiteImage.Height;
31
32 //设定最终图片的尺寸
33 int f_width = Math.Max(b_width, w_width);
34 int f_height = Math.Max(b_height, w_height);
35
36 Bitmap result = new Bitmap(f_width, f_height);
37
38 //黑色图片距离边缘的距离
39 int b_widthOffset = b_width == f_width ? 0 : (f_width - b_width) / 2;
40 int b_heightOffset = b_height == f_height ? 0 : (f_height - b_height) / 2;
41
42 //白色图片离边缘距离
43 int w_widthOffset = w_width == f_width ? 0 : (f_width - w_width) / 2;
44 int w_heightOffset = w_height == f_height ? 0 : (f_height - w_height) / 2;
45
46 for (int x = 0; x < f_width; x++) {
47 for (int y = 0; y < f_height; y++) {
48 //上下左右交叉排列黑白像素
49 bool blackPixel = (x + y) % 2 == 0 ? true : false;
50
51 int coor_x;
52 int coor_y;
53 //决定当前像素位置是否对应图一或图二某像素，如果没有，跳过循环
54 bool validPixel = true;
55 if (blackPixel) {
56 coor_x = x - b_widthOffset;
57 if (coor_x > b_width - 1) validPixel = false;
58 coor_y = y - b_heightOffset;
59 if (coor_y > b_height - 1) validPixel = false;
60 } else {
61 coor_x = x - w_widthOffset;
62 if (coor_x > w_width - 1) validPixel = false;
63 coor_y = y - w_heightOffset;
64 if (coor_y > w_height - 1) validPixel = false;
65 }
66
67 validPixel = validPixel && coor_x >= 0 && coor_y >= 0;
68 if (!validPixel) continue;
69
70 //根据颜色计算像素灰度，设定透明度
71 if (blackPixel) {
72 Color origin = blackImage.GetPixel(coor_x, coor_y);
73 int gray = (origin.R * 19595 + origin.G * 38469 + origin.B * 7472) >> 16;
74 Color finalColor = Color.FromArgb(255 - gray, Color.Black);
75 result.SetPixel(x, y, finalColor);
76 } else {
77 Color origin = whiteImage.GetPixel(coor_x, coor_y);
78 int gray = (origin.R * 19595 + origin.G * 38469 + origin.B * 7472) >> 16;
79 Color finalColor = Color.FromArgb(gray, Color.White);
80 result.SetPixel(x, y, finalColor);
81 }
82 }
83 }
84
85 return result;
86 }
87 }
通过jQuery和C#分别实现对.NET Core Web Api的访问以及文件上传
准备工作：
建立.NET Core Web Api项目
新建一个用于Api请求的UserInfo类
public class UserInfo
{
public string name { get; set; }
public int age { get; set; }
public bool sex { get; set; }
}
2、建立.NET Core Web项目
一、使用jQuery Ajax访问
（一）、表单 [FromForm]
数据类型：Object
ContenyType类型：application/x-www-form-urlencoded
var model = { name: "刘大大", age: 23, sex: true };
前台请求
var model = { name: "刘大大", age: 23, sex: true };
$.ajax({
url: "http://localhost:57954/API/Default/data",
type: "POST",
async: true,
dataType: "json",
data: model,
contentType: "application/x-www-form-urlencoded",
success: function (data) {
console.log("data:");
console.log(data);
}
});
后台接受
（二）、JSON字符串 [FromBdy]
数据类型：Json
ContenyType类型：application/json
var json={"name":"刘大大","age":23,"sex":true}
也可以使用JSON.stringify(Object)将Object转换为JSON字符串
前端请求
var model = { name: "刘大大", age: 23, sex: true };
$.ajax({
url: "http://localhost:57954/API/Default/data",
type: "POST",
async: true,
dataType: "json",
data: JSON.stringify(model),
contentType: "application/json",
success: function (data) {
console.log("data:");
console.log(data);
}
});
后台接受
（三）、文件上传
建立FormData对象
数据类型：FromData
ContenyType类型false, //必须false才会避开jQuery对 formdata 的默认处理
processData类型: false, //必须false才会自动加上正确的Content-Type
html
<input type="file" multiple id="file" />
JS获取文件对象
var file = document.getElementById("file");
var files = file.files;
var formData = new FormData();
for (var i = 0; i < files.length; i++) {
formData.append(files[i].name, files[i]);
} formData.append("name", "刘大大");//可追加参数
AJAX请求
$.ajax({
url: "http://localhost:57954/API/Default/data",
type: "POST",
async: true,
dataType: "json",
data: formData,
contentType: false,
processData: false,
success: function (data) {
console.log("data:");
console.log(data);
}
});
后台接受
追加的name参数
传输的文件
二、使用C#后台访问
（一）、Get访问
var url = "http://localhost:57954/API/Default/values";
using (var client = new HttpClient(new HttpClientHandler() { AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip }))
{
var taskResponse = client.GetAsync(url);
taskResponse.Wait();
if (taskResponse.IsCompletedSuccessfully)
{
var taskStream = taskResponse.Result.Content.ReadAsStreamAsync();
taskStream.Wait();
using (var reader = new StreamReader(taskStream.Result))
{
jsonString = reader.ReadToEnd();
}
}
}
（二）、Post访问
var data = new {name="刘大大",age=23,sex=true };
using (var client = new HttpClient(new HttpClientHandler() { AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip }))
{
var jsonToSend = JsonConvert.SerializeObject(data, Formatting.None, new IsoDateTimeConverter());
var body = new StringContent(jsonToSend, Encoding.UTF8, "application/json");
var taskResponse = client.PostAsync(url, body);
taskResponse.Wait();
if (taskResponse.IsCompletedSuccessfully)
{
var taskStream = taskResponse.Result.Content.ReadAsStreamAsync();
taskStream.Wait();
using (var reader = new StreamReader(taskStream.Result))
{
jsonString = reader.ReadToEnd();
}
}
}
（三）、上传文件
public IActionResult Upload()
{
var url = "http://localhost:57954/API/Default/values";
var data = new MultipartFormDataContent();
if (Request.HasFormContentType)
{
var request = Request.Form.Files;
foreach (var item in request)
{
data.Add(new StreamContent(item.OpenReadStream()), item.Name, item.FileName);
}
foreach (var item in Request.Form)
{
data.Add(new StringContent(item.Value), item.Key);
}
}
string jsonString;
using (var client = new HttpClient(new HttpClientHandler() { AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip }))
{
var taskResponse = client.PostAsync(url, data);
taskResponse.Wait();
if (taskResponse.IsCompletedSuccessfully)
{
var taskStream = taskResponse.Result.Content.ReadAsStreamAsync();
taskStream.Wait();
using (var reader = new StreamReader(taskStream.Result))
{
jsonString = reader.ReadToEnd();
}
}
}
return Json("OK");
}
WebHelper
这里包含了WebRequest和HttpClient两种请求方式，以及包含了将Object对象序列化为HttpCotnent对象的方法。
/***************************************************************************************************************************************************
* *文件名：WebHelper.cs
* *创建人：Jon
* *日 期 ：2018年5月25日
* *描 述 ：实现HTTP协议中的GET、POST请求
* *MVC使用HttpClient上传文件实例：
public IActionResult Upload()
{
var url = "http://localhost:57954/API/Default/values";
var data = new MultipartFormDataContent();
if (Request.HasFormContentType)
{
var request = Request.Form.Files;
foreach (var item in request)
{
data.Add(new StreamContent(item.OpenReadStream()), item.Name, item.FileName);
}
foreach (var item in Request.Form)
{
data.Add(new StringContent(item.Value), item.Key);
}
}
WebHelper.PostByHttpClientFromHttpContent(url, data);
return Json("OK");
}
*****************************************************************************************************************************************************/
using Newtonsoft.Json;
using Newtonsoft.Json.Converters;
using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
namespace Expansion.Helper
{
public static class WebHelper
{
/// <summary>
/// 通过WebRequest发起Get请求
/// </summary>
/// <param name="url">请求地址</param>
/// <returns>JSON字符串</returns>
public static string GetByWebRequest(string url)
{
string jsonString = string.Empty;
var request = (HttpWebRequest)WebRequest.Create(url);
request.Method = "GET";
request.ContentType = "application/json";
request.AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip;
var response = (HttpWebResponse)request.GetResponse();
using (var stream = new StreamReader(response.GetResponseStream()))
{
jsonString = stream.ReadToEnd();
}
return jsonString;
}
/// <summary>
/// 通过WebRequest发起Post请求
/// </summary>
/// <param name="url">请求地址</param>
/// <param name="data">请求参数</param>
/// <returns>JSON字符串</returns>
public static string PostByWebRequest(string url, object data)
{
string jsonString = string.Empty;
var request = (HttpWebRequest)WebRequest.Create(url);
request.ContentType = "application/json";
request.Method = "POST";
request.Timeout = Int32.MaxValue;
request.AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip;
var jsonToSend = JsonConvert.SerializeObject(data, Formatting.None, new IsoDateTimeConverter());
byte[] btBodys = Encoding.UTF8.GetBytes(jsonToSend);
request.ContentLength = btBodys.Length;
request.GetRequestStream().Write(btBodys, 0, btBodys.Length);
var response = (HttpWebResponse)request.GetResponse();
using (var stream = new StreamReader(response.GetResponseStream()))
{
jsonString = stream.ReadToEnd();
}
return jsonString;
}
/// <summary>
/// 通过HttpClient发起Get请求
/// </summary>
/// <param name="url">请求地址</param>
/// <returns>JSON字符串</returns>
public static string GetByHttpClient(string url)
{
string jsonString = string.Empty;
using (var client = new HttpClient(new HttpClientHandler() { AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip }))
{
var taskResponse = client.GetAsync(url);
taskResponse.Wait();
if (taskResponse.IsCompletedSuccessfully)
{
var taskStream = taskResponse.Result.Content.ReadAsStreamAsync();
taskStream.Wait();
using (var reader = new StreamReader(taskStream.Result))
{
jsonString = reader.ReadToEnd();
}
}
}
return jsonString;
}
/// <summary>
/// 通过HttpClient发起Post请求
/// </summary>
/// <param name="url">请求地址</param>
/// <param name="data">请求参数</param>
/// <returns>JSON字符串</returns>
public static string PostByHttpClient(string url, object data)
{
string jsonString = string.Empty;
using (var client = new HttpClient(new HttpClientHandler() { AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip }))
{
var jsonToSend = JsonConvert.SerializeObject(data, Formatting.None, new IsoDateTimeConverter());
var body = new StringContent(jsonToSend, Encoding.UTF8, "application/json");
var taskResponse = client.PostAsync(url, body);
taskResponse.Wait();
if (taskResponse.IsCompletedSuccessfully)
{
var taskStream = taskResponse.Result.Content.ReadAsStreamAsync();
taskStream.Wait();
using (var reader = new StreamReader(taskStream.Result))
{
jsonString = reader.ReadToEnd();
}
}
}
return jsonString;
}
/// <summary>
/// 通过数据来自HttpContent的HttpClient发起Post请求
/// </summary>
/// <param name="url">请求地址</param>
/// <param name="content">请求参数</param>
/// <returns>JSON字符串</returns>
public static string PostByHttpClientFromHttpContent(string url, HttpContent content)
{
string jsonString = string.Empty;
using (var client = new HttpClient(new HttpClientHandler() { AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip }))
{
var taskResponse = client.PostAsync(url, content);
taskResponse.Wait();
if (taskResponse.IsCompletedSuccessfully)
{
var taskStream = taskResponse.Result.Content.ReadAsStreamAsync();
taskStream.Wait();
using (var reader = new StreamReader(taskStream.Result))
{
jsonString = reader.ReadToEnd();
}
}
}
return jsonString;
}
/// <summary>
/// Object转换为StreamContent
/// </summary>
/// <param name="data">请求参数</param>
/// <returns>StreamContent</returns>
public static HttpContent ToStreamContent(this object data)
{
var json = JsonConvert.SerializeObject(data, Formatting.None, new IsoDateTimeConverter());
byte[] bytes = Encoding.UTF8.GetBytes(json);
MemoryStream ms = new MemoryStream();
ms.Write(bytes, 0, bytes.Length);
ms.Position = 0;
HttpContent streamContent = new StreamContent(ms);
return streamContent;
}
/// <summary>
/// Object转换为StringContent
/// </summary>
/// <param name="data">请求参数</param>
/// <returns>StringContent</returns>
public static HttpContent ToStringContent(this object data)
{
HttpContent stringContent = new StringContent(JsonConvert.SerializeObject(data));
return stringContent;
}
/// <summary>
/// Object转换为MultipartFormDataContent
/// </summary>
/// <param name="data"></param>
/// <returns>MultipartFormDataContent</returns>
public static HttpContent ToMultipartFormDataContent(this object data)
{
var json = JsonConvert.SerializeObject(data, Formatting.None, new IsoDateTimeConverter());
var body = new StringContent(json, Encoding.UTF8, "application/json");
var multipartFormDataContent = new MultipartFormDataContent();
multipartFormDataContent.Add(body);
return multipartFormDataContent;
}
/// <summary>
/// Object转换为FormUrlEncodedContent
/// </summary>
/// <param name="data">请求参数</param>
/// <returns>FormUrlEncodedContent</returns>
public static HttpContent ToFormUrlEncodedContent(this object data)
{
var param = new List<KeyValuePair<string, string>>();
var values = JObject.FromObject(data);
foreach (var item in values)
{
param.Add(new KeyValuePair<string, string>(item.Key, item.Value.ToString()));
}
HttpContent formUrlEncodedContent = new FormUrlEncodedContent(param);
return formUrlEncodedContent;
}
/// <summary>
/// Object转换为ByteArrayContent
/// </summary>
/// <param name="data">请求参数</param>
/// <returns>FormUrlEncodedContent</returns>
public static HttpContent ToByteArrayContent(this object data)
{
var json = JsonConvert.SerializeObject(data, Formatting.None, new IsoDateTimeConverter());
byte[] bytes = Encoding.UTF8.GetBytes(json);
HttpContent byteArrayContent = new ByteArrayContent(bytes);
return byteArrayContent;
}
/// <summary>
/// Url编码
/// </summary>
/// <param name="content">内容</param>
/// <param name="encode">编码类型</param>
/// <returns></returns>
private static string Encode(string content, Encoding encode = null)
{
if (encode == null) return content;
return System.Web.HttpUtility.UrlEncode(content, Encoding.UTF8);
}
/// <summary>
/// Url解码
/// </summary>
/// <param name="content">内容</param>
/// <param name="encode">编码类型</param>
/// <returns></returns>
private static string Decode(string content, Encoding encode = null)
{
if (encode == null) return content;
return System.Web.HttpUtility.UrlDecode(content, Encoding.UTF8);
}
/// <summary>
/// 将键值对参数集合拼接为Url字符串
/// </summary>
/// <param name="paramArray">键值对集合</param>
/// <param name="encode">转码类型</param>
/// <returns></returns>
private static string BuildParam(List<KeyValuePair<string, string>> paramArray, Encoding encode = null)
{
string url = "";
if (encode == null) encode = Encoding.UTF8;
if (paramArray != null && paramArray.Count > 0)
{
var parms = "";
foreach (var item in paramArray)
{
parms += string.Format("{0}={1}&", Encode(item.Key, encode), Encode(item.Value, encode));
}
if (parms != "")
{
parms = parms.TrimEnd('&');
}
url += parms;
}
return url;
}
}
}
时间仓促，没能说的太详细，有时间再做补充。如本文中的有错误示范，欢迎指正