How to post image using Arduino HTTPClient
Below is the perfectly working code I got from here.
#include &lt;Arduino.h&gt;
#include &lt;WiFi.h&gt;
#include &quot;soc/soc.h&quot;
#include &quot;soc/rtc_cntl_reg.h&quot;
#include &quot;esp_camera.h&quot;

const char* ssid = &quot;REPLACE_WITH_YOUR_SSID&quot;;
const char* password = &quot;REPLACE_WITH_YOUR_PASSWORD&quot;;

String serverName = &quot;192.168.1.XXX&quot;;   // REPLACE WITH YOUR Raspberry Pi IP ADDRESS
//String serverName = &quot;example.com&quot;;   // OR REPLACE WITH YOUR DOMAIN NAME

String serverPath = &quot;/upload.php&quot;;     // The default serverPath should be upload.php

const int serverPort = 80;

WiFiClient client;

// CAMERA_MODEL_AI_THINKER
#define PWDN_GPIO_NUM     32
#define RESET_GPIO_NUM    -1
#define XCLK_GPIO_NUM      0
#define SIOD_GPIO_NUM     26
#define SIOC_GPIO_NUM     27

#define Y9_GPIO_NUM       35
#define Y8_GPIO_NUM       34
#define Y7_GPIO_NUM       39
#define Y6_GPIO_NUM       36
#define Y5_GPIO_NUM       21
#define Y4_GPIO_NUM       19
#define Y3_GPIO_NUM       18
#define Y2_GPIO_NUM        5
#define VSYNC_GPIO_NUM    25
#define HREF_GPIO_NUM     23
#define PCLK_GPIO_NUM     22

const int timerInterval = 30000;    // time between each HTTP POST image
unsigned long previousMillis = 0;   // last time image was sent

void setup() {
  WRITE_PERI_REG(RTC_CNTL_BROWN_OUT_REG, 0); 
  Serial.begin(115200);

  WiFi.mode(WIFI_STA);
  Serial.println();
  Serial.print(&quot;Connecting to &quot;);
  Serial.println(ssid);
  WiFi.begin(ssid, password);  
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(&quot;.&quot;);
    delay(500);
  }
  Serial.println();
  Serial.print(&quot;ESP32-CAM IP Address: &quot;);
  Serial.println(WiFi.localIP());

  camera_config_t config;
  config.ledc_channel = LEDC_CHANNEL_0;
  config.ledc_timer = LEDC_TIMER_0;
  config.pin_d0 = Y2_GPIO_NUM;
  config.pin_d1 = Y3_GPIO_NUM;
  config.pin_d2 = Y4_GPIO_NUM;
  config.pin_d3 = Y5_GPIO_NUM;
  config.pin_d4 = Y6_GPIO_NUM;
  config.pin_d5 = Y7_GPIO_NUM;
  config.pin_d6 = Y8_GPIO_NUM;
  config.pin_d7 = Y9_GPIO_NUM;
  config.pin_xclk = XCLK_GPIO_NUM;
  config.pin_pclk = PCLK_GPIO_NUM;
  config.pin_vsync = VSYNC_GPIO_NUM;
  config.pin_href = HREF_GPIO_NUM;
  config.pin_sscb_sda = SIOD_GPIO_NUM;
  config.pin_sscb_scl = SIOC_GPIO_NUM;
  config.pin_pwdn = PWDN_GPIO_NUM;
  config.pin_reset = RESET_GPIO_NUM;
  config.xclk_freq_hz = 20000000;
  config.pixel_format = PIXFORMAT_JPEG;

  // init with high specs to pre-allocate larger buffers
  if(psramFound()){
    config.frame_size = FRAMESIZE_SVGA;
    config.jpeg_quality = 10;  //0-63 lower number means higher quality
    config.fb_count = 2;
  } else {
    config.frame_size = FRAMESIZE_CIF;
    config.jpeg_quality = 12;  //0-63 lower number means higher quality
    config.fb_count = 1;
  }
  
  // camera init
  esp_err_t err = esp_camera_init(&amp;config);
  if (err != ESP_OK) {
    Serial.printf(&quot;Camera init failed with error 0x%x&quot;, err);
    delay(1000);
    ESP.restart();
  }

  sendPhoto(); 
}

void loop() {
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis &gt;= timerInterval) {
    sendPhoto();
    previousMillis = currentMillis;
  }
}

String sendPhoto() {
  String getAll;
  String getBody;

  camera_fb_t * fb = NULL;
  fb = esp_camera_fb_get();
  if(!fb) {
    Serial.println(&quot;Camera capture failed&quot;);
    delay(1000);
    ESP.restart();
  }
  
  Serial.println(&quot;Connecting to server: &quot; + serverName);

  if (client.connect(serverName.c_str(), serverPort)) {
    Serial.println(&quot;Connection successful!&quot;);    
    String head = &quot;--RandomNerdTutorials\r\nContent-Disposition: form-data; name=\&quot;imageFile\&quot;; filename=\&quot;esp32-cam.jpg\&quot;\r\nContent-Type: image/jpeg\r\n\r\n&quot;;
    String tail = &quot;\r\n--RandomNerdTutorials--\r\n&quot;;

    uint16_t imageLen = fb-&gt;len;
    uint16_t extraLen = head.length() + tail.length();
    uint16_t totalLen = imageLen + extraLen;
  
    client.println(&quot;POST &quot; + serverPath + &quot; HTTP/1.1&quot;);
    client.println(&quot;Host: &quot; + serverName);
    client.println(&quot;Content-Length: &quot; + String(totalLen));
    client.println(&quot;Content-Type: multipart/form-data; boundary=RandomNerdTutorials&quot;);
    client.println();
    client.print(head);
  
    uint8_t *fbBuf = fb-&gt;buf;
    size_t fbLen = fb-&gt;len;
    for (size_t n=0; n&lt;fbLen; n=n+1024) {
      if (n+1024 &lt; fbLen) {
        client.write(fbBuf, 1024);
        fbBuf += 1024;
      }
      else if (fbLen%1024&gt;0) {
        size_t remainder = fbLen%1024;
        client.write(fbBuf, remainder);
      }
    }   
    client.print(tail);
    
    esp_camera_fb_return(fb);
    
    int timoutTimer = 10000;
    long startTimer = millis();
    boolean state = false;
    
    while ((startTimer + timoutTimer) &gt; millis()) {
      Serial.print(&quot;.&quot;);
      delay(100);      
      while (client.available()) {
        char c = client.read();
        if (c == '\n') {
          if (getAll.length()==0) { state=true; }
          getAll = &quot;&quot;;
        }
        else if (c != '\r') { getAll += String(c); }
        if (state==true) { getBody += String(c); }
        startTimer = millis();
      }
      if (getBody.length()&gt;0) { break; }
    }
    Serial.println();
    client.stop();
    Serial.println(getBody);
  }
  else {
    getBody = &quot;Connection to &quot; + serverName +  &quot; failed.&quot;;
    Serial.println(getBody);
  }
  return getBody;
}