How to pick up Hi-Resolution Image from Amazon product page

Recently I realized that Amazon offers high resolution photos in some products.
I have found the way to extract these hires images.
Note Note!: This method might be unavailable in the future because Amazon may not like this kind of hack or change the implementation :P

Basic Strategy

For example, this page:
http://www.amazon.com/Silver-Violin-Nicola-Benedetti/dp/B008CYV046/
If you see the html source of this page, you can find the following json string.

var colorImages = {"initial":[{"large":"http://ecx.images-amazon.com/images/I/XXXXXXX.jpg",....

It represents the urls of various size of images.
If you would like to see the hi-resolution image, you should pick up the url which is defined in hiRes property.

Source Code

You know I still like Java, I will show you the simple Java code.
I use Jackson for parsing JSon string.

import java.io.IOException;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import com.dukesoftware.utils.common.AmazonImageInHtmlFinder.AmazonImageUrl;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;


public class AmazonImageService {

    // pattern for finding JSon string which has hires image url.
    private static final Pattern AMAZON_HIRES_IMAGE_JSON_PATTERN 
                                       = Pattern.compile("var\\s+colorImages\\s*=\\s*(\\{.+\\});");

    // some cleanup pattern
    private static final Pattern PATTERN_REMOVE_AMAZON_SIZE = Pattern.compile("\\._[\\w0-9]{1,6}_");
    
    private final ObjectMapper mapper;
    
    public AmazonImageService()
    {
        this(new ObjectMapper());
    }
    
    public AmazonImageService(ObjectMapper mapper)
    {
        this.mapper = mapper;

        // a bit important part: Since I would like to minimize the pojo, I configure like this - ignore unknown properties.
        this.mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    }
    
    public List<AmazonImageUrl> getImages(String asin)
            throws URISyntaxException, IOException, JsonParseException,
            JsonMappingException {
        String url = toAmazonUrl(asin);
        String content = getStringContentsFromURL(url, "utf-8");
        String jsonStr = extractJSon(content);
        Map<String, List<AmazonImageUrl>> map 
                   = mapper.readValue(jsonStr, new TypeReference<Map<String, List<AmazonImageUrl>>>() {});
        List<AmazonImageUrl> resultUrls = extractImageUrls(map);
        cleanup(resultUrls);
        return resultUrls;
    }

    private static void cleanup(List<AmazonImageUrl> resultUrls) {
        for(AmazonImageUrl resultUrl : resultUrls)
        {
            if(resultUrl.getHiRes() != null)
            {
                resultUrl.setHiRes(PATTERN_REMOVE_AMAZON_SIZE.matcher(resultUrl.getHiRes()).replaceAll("").trim());
            }
        }
    }

    private static List<AmazonImageUrl> extractImageUrls(
            Map<String, List<AmazonImageUrl>> map) {
        List<AmazonImageUrl> resultUrls = new ArrayList<AmazonImageUrl>();
        
        for(List<AmazonImageUrl> imageDataList : map.values())
        {
            for(AmazonImageUrl imageData : imageDataList)
            {
                if(imageData.getHiRes() != null || imageData.getLarge() != null)
                {
                    resultUrls.add(imageData);
                }
            }
        }
        return resultUrls;
    }

    private static String extractJSon(String content) {
        Matcher matcher = AMAZON_HIRES_IMAGE_JSON_PATTERN.matcher(content);
        String jsonStr = "{}";
        if(matcher.find())
        {
            jsonStr = matcher.group(1);
        }
        return jsonStr;
    }

    private static String toAmazonUrl(String asin) {
        return "http://www.amazon.com/product/dp/"+asin+"/";
    }


    // Java pojo class for mapped from JSon object.
    public static class AmazonImageUrl{
        private String hiRes;
        private String large;

        public String getHiRes() {
            return hiRes;
        }

        public void setHiRes(String hiRes) {
            this.hiRes = hiRes;
        }
        
        public String getLarge() {
            return large;
        }

        public void setLarge(String large) {
            this.large = large;
        }

        @Override
        public String toString() {
            return hiRes;
        }
    }


    // trivial utility methods....
    // you can use java commons library etc...
    private static String getStringContentsFromURL(String u, String charset) throws URISyntaxException, IOException {
     URL url = new URL(u);
     HttpURLConnection connection = null;
     try{
      connection = (HttpURLConnection)url.openConnection();
      return toString(connection.getInputStream(), charset);
     }
     finally{
            if(connection != null){
                connection.disconnect();
            }
     }
    }

    private static String toString(InputStream is, String charsetName) throws IOException {   
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        copy(is, baos, _1K_BYTES);
        return baos.toString(charsetName);
    }

    private final static void copy(InputStream is, OutputStream os, int bufsize) throws IOException {
        copy(is, os, new byte[bufsize]);
    }

    private final static void copy(InputStream is, OutputStream os, byte[] buffer)throws IOException {
        try{
            for (int bytes = 0 ;(bytes = is.read(buffer)) != -1; ) 
            {
                os.write(buffer, 0, bytes);
            }
            os.flush();
        }finally{
            closeQuietly(is);
        }
    }
}

The Usage of the AmazonImageService class is quite simple.

String asin = "XXXXXXXX";
List images = new AmazonImageService().getImages(asin);