Sign Ripple transaction locally using ripple-lib-java

Since rippled 1.1.0 disables public signing by default, we either need to host our own API server or sign Ripple transaction locally. Fortunately, ripple-lib-java gives clue on how to do this in one of its example. Long story short, we can use this simple method to do the signing: import java.math.BigDecimal; import com.ripple.core.types.known.tx.txns.Payment; import com.ripple.core.types.known.tx.signed.SignedTransaction;…

Existing PHP catches and bugs

I will keep updating this post as part of note whenever I find another catch and bug in PHP. I hope it can help beginner PHP developers (like me) out there to escape hours of confusion and stress .. 😅 PUT multipart/data bug As explained by this open bug (since 2011), when you submit a multipart/data…

SIFT/SURF BoW for big number of clusters

If you spend some time browsing, there are some examples already available for Python SIFT/SURF bag of words (BoW) classifier in the internet. They use clustering (usually K-Means) to build dictionary of visual vocabularies (usually with sklearn or cv2 clustering library) of SIFT/SURF features. However, most of the sample codes that I found can’t properly…

Simple music fingerprinting using Chromaprint in Python

Have you ever heard or even use service like Shazam? Cool, right? No, we are not going to make something as magical as it 😜 But using chromaprint we can create audio fingerprint so that we can do music search by using a music sample. Before we can use chromaprint python library, pyacoustid, we need to install chromaprint…

Keras VGG16 flat-features extractor

Using pre-trained deep learning model as feature extractor is a proven way to improve classification accuracy. One of the famous model is Oxford’s VGG16, which is trained using million images to recognize 1,000 classes ranging from animals, vehicles and other stuffs. Now, to use VGG16 as part of another neural network is relatively easy, especially…

Check balance and send Ripple (XRP) using Java

Update: As mentioned in here, since rippled 1.1.0 remote sign API is not allowed by default anymore. If you try to call it on wss://s.altnet.rippletest.net:51233 you will get “Signing is not supported by this server” error. Check this post on how to sign transaction locally using Java Ripple (XRP) provides some options to interact with their…

Hello WordPress!

Update: I gave up on the markdown plugin as it does not work as smooth as github’s. I also found better themes. Yes,  I can easily change my mind over trivial things 😜 So I got bored with ghost and decided to use WordPress for my blog. Luckily, I found a nice markdown plugin and an…

Node.js – smart contract integration with truffle-contract and infura.io

While running your own Ethereum node with geth by using web3js from node.js (backend) app is a common solution, connecting to a public Ethereum node such as infura.io and using [truffle-contract](https://github.com/trufflesuite/truffle-contract] gives some benefits: No need to maintain your own Ethereum node (syncing a full node requires huge storage space! (around 40 GB for Ropsten))…

Sending Bitcoin programmatically using BlockCypher API

BlockCypher provides convenient REST APIs to send cryptocurrency like Bitcoin easily. Here are two APIs that we can use to send Bitcoin from one address to another: 1. Build transaction skeleton https://api.blockcypher.com/v1/btc/test3/txs/new 2. Push signed transaction https://api.blockcypher.com/v1/btc/test3/txs/send Here are the step by steps of using those APIs in JavaScript (Node.js) in testnet3 Bitcoin network. First,…