Downloading an image from twitter with libcurl C++

Question

I'm making a program that takes a person's tweet, and if it contains an image, download it.

Why can I download an image from this URL (Example #1)
http://www.google.co.id/intl/en_com/images/logo_plain.png
And not from this URL (Example #2)
https://www.google.com/imgres?imgurl=https://pbs.twimg.com/media/DR-kkH4XcAAQ-vc.jpg&imgrefurl=https://twitter.com/officialmcafee/status/945655402276024320&h=1200&w=992&tbnid=0q3B6ZB_UxjRIM&tbnh=247&tbnw=204&usg=__xvjbjSSMvuImESBLVvBBrUagUe8=&docid=vdqkoUmaefYoFM

Example #1

#include <iostream> 
#include <curl/curl.h> 

using namespace std;
int main()
{
    CURL *image;
    CURLcode imgresult;
    FILE *fp = nullptr;
    const char *url = "http://www.google.co.id/intl/en_com/images/logo_plain.png";
    image = curl_easy_init();
    if (image)
    {
        // Open file 
        fp = fopen("img.png", "wb");
        if (fp == NULL) cout << "File cannot be opened";

        curl_easy_setopt(image, CURLOPT_WRITEFUNCTION, NULL);
        curl_easy_setopt(image, CURLOPT_WRITEDATA, fp);
        curl_easy_setopt(image, CURLOPT_URL, url);
        // Grab image 
        imgresult = curl_easy_perform(image);
        if (imgresult)
            cout << "Cannot grab the image!\n";
    }
    // Clean up the resources 
    curl_easy_cleanup(image);
    // Close the file 
    fclose(fp);
    system("pause");
    return 0;
}

Example #2

#include <iostream> 
#include <curl/curl.h> 

using namespace std;
int main()
{
    CURL *image;
    CURLcode imgresult;
    FILE *fp = nullptr;
    const char *url = "https://www.google.com/imgres?imgurl=https://pbs.twimg.com/media/DR-kkH4XcAAQ-vc.jpg&imgrefurl=https://twitter.com/officialmcafee/status/945655402276024320&h=1200&w=992&tbnid=0q3B6ZB_UxjRIM&tbnh=247&tbnw=204&usg=__xvjbjSSMvuImESBLVvBBrUagUe8=&docid=vdqkoUmaefYoFM";
    image = curl_easy_init();
    if (image)
    {
        // Open file 
        fp = fopen("img.png", "wb");
        if (fp == NULL) cout << "File cannot be opened";

        curl_easy_setopt(image, CURLOPT_WRITEFUNCTION, NULL);
        curl_easy_setopt(image, CURLOPT_WRITEDATA, fp);
        curl_easy_setopt(image, CURLOPT_URL, url);
        // Grab image 
        imgresult = curl_easy_perform(image);
        if (imgresult)
            cout << "Cannot grab the image!\n";
    }
    // Clean up the resources 
    curl_easy_cleanup(image);
    // Close the file 
    fclose(fp);
    system("pause");
    return 0;
}

Answer 1

First, this is not a link to an image. This is html page. Note, that your code doesn't download any image the html page refers to, but just html page.

Second, you are not following redirects. Add one more option:

curl_easy_setopt(image, CURLOPT_FOLLOWLOCATION, 1);

Third, you'd better to pretend to be a browser:

curl_easy_setopt(image, CURLOPT_USERAGENT, "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.94 Safari/537.36");

Once I added both options, I managed to download your link.