Skip to main content

### Enabling Imagick to Read or Manipulate PDF File

Imagick is one of the popular tools for manipulating image files. Some popular languages such as PHP and Node.js have provided libraries that can be used for manipulating images based on Imagick. One of the common use cases for using Imagick is for generating a thumbnail from an image or PDF file.

In PHP, we can install the PHP Imagick module by running the following command.

apt install php-imagick

Then, we can verify the installation by running this command.

php -m | grep imagick

For example, we want to generate a thumbnail image for a PDF file in PHP. We can use the following script.

<?php
$im = new Imagick();$im->setResolution(50, 50); // set the reading resolution before read the file
$im->readImage('file.pdf[0]'); // read the first page of the PDF file (index 0) //$im = $im->flattenImages(); // @deprecated // handle transparency problem$im = $im->mergeImageLayers( Imagick::LAYERMETHOD_FLATTEN );$im->setImageFormat('png');
$im->writeImage('file.png'); If we want to set a specific size for the thumbnail. We can run the following script after flattening the image. <?php$imageprops = $im->getImageGeometry();$width = $imageprops['width'];$height = $imageprops['height'];$baseHeight = 500;
$baseWidth = 250; if($width > $height){$newHeight = $baseHeight;$newWidth = ceil($baseHeight *$width / $height); }else{$newWidth = $baseWidth;$newHeight = ceil($baseWidth *$height / $width); }$im->resizeImage($newWidth,$newHeight, imagick::FILTER_LANCZOS, 0.9, true);

If we run the code above, PHP may throw an error that says something like:

ImagickException: not authorized file.pdf' @ error/constitute.c/ReadImage/412

It is caused by the restriction policy of Imagick for a PDF file. A PDF file may contain a script (PostScript) that can perform harmful actions. Imagick utilizes GhostScript for interpreting scripts in a PDF file. We can configure the Imagick operation policy for specific file types by modifying the /etc/ImageMagick-6/policy.xml file. You can read more detail about it here. Find the following declaration and modify it as you require.

<policy domain="coder" rights="none" pattern="EPS" />
<!--policy domain="coder" rights="none" pattern="PDF" /-->
<policy domain="coder" rights="none" pattern="XPS" />
<policy domain="coder" rights="read|write" pattern="PDF,PS" />


If we use PHP in a Windows environment, there are several procedures to make our program can result in the desired outcome.

Firstly, we need to download the DLL files of Imagick from the PECL site. The folder contains a lot of DLL files, not only the php_imagick.dll file but also other files required by the operating systems. We can put the files in a subdirectory of the PHP ext directory, for example, we put them in ext/imagick.

Because it is not a standard directory for a PHP dynamic module, we configure the declaration of its usages using an absolute path in php.ini.

[Imagick]
extension="C:\path\to\php\ext\imagick\php_imagick.dll"


Next step, we add a new record in the PATH environment variable by location of the Imagick supported DLL files which is C:\path\to\php\ext\imagick.

After the previous step, if we run the program, PHP still throws an error with a message that looks like this:

PDFDelegateFailed The system cannot find the file specified. ' @ error/pdf.c/ReadPDFImage/801

It is caused by the absence of GhostScript support. So the last step, we need to download and install the GhostScript application from here. Then, we must add the bin directory in the GhostScript installation folder into the PATH environment variable. If we use a 64bit version, we need to make a copy of gswin64.exe and rename the copy into gs.exe. It is because Imagick will look for gs.exe.

### Rangkaian Sensor Infrared dengan Photo Dioda

Keunggulan photodioda dibandingkan LDR adalah photodioda lebih tidak rentan terhadap noise karena hanya menerima sinar infrared, sedangkan LDR menerima seluruh cahaya yang ada termasuk infrared. Rangkaian yang akan kita gunakan adalah seperti gambar di bawah ini. Pada saat intensitas Infrared yang diterima Photodiode besar maka tahanan Photodiode menjadi kecil, sedangkan jika intensitas Infrared yang diterima Photodiode kecil maka tahanan yang dimiliki photodiode besar. Jika  tahanan photodiode kecil  maka tegangan  V- akan kecil . Misal tahanan photodiode mengecil menjadi 10kOhm. Maka dengan teorema pembagi tegangan: V- = Rrx/(Rrx + R2) x Vcc V- = 10 / (10+10) x Vcc V- = (1/2) x 5 Volt V- = 2.5 Volt Sedangkan jika  tahanan photodiode besar  maka tegangan  V- akan besar  (mendekati nilai Vcc). Misal tahanan photodiode menjadi 150kOhm. Maka dengan teorema pembagi tegangan: V- = Rrx/(Rrx + R2) x Vcc V- = 150 / (150+10) x Vcc V- = (150/160) x 5

### Kerusakan pada Motherboard

1. Sering terjadi hang memory tidak cocok --- ganti memory ada virus di harddisk --- scan harddisk over clock --- seting kembali clock prosesor ada bad sector di harddisk --- partisi harddisk dengan benar 2. Pembacaan data menjadi lambat memori tidak cukup --- tambah memori harddisk penuh atau ada virus --- kurangi isi harddisk, scan harddisk, atau ganti hardisk 3. CMOS failure baterai habis --- ganti baterai CMOS seting BIOS berubah --- seting kembali BIOS 4. Tidak bisa booting cache memory rusak --- disable eksternal cache memory di BIOS memori tidak cocok --- ganti memori boot sector pada harddisk rusak --- masukkan operating system baru ada bad sector pada trek awal harddisk --- partisi harddisk 5. Suara bip panjang berkali-kali memori rusak --- periksa kedudukan memori memori tidak cocok --- ganti memori memori tidak masuk slot dengan sempurna --- periksa kembali kedudukan memori 6. Suara bip bagus tetapi tidak ada tampilan / bip dua kali VGA card

### Raspberry Pi Bluetooth Connection

Raspberry Pi 3 provides a built-in Bluetooth module. The latest Raspbian has been bundled with tools for enabling Bluetooth connection. The Bluetooth icon will be shown up on the top right corner of the desktop. It's a tool to discover available Bluetooth devices and connect Pi with Bluetooth devices. It is easy to connect any Bluetooth-enabled electronic device with Pi. But, sometimes Pi will fail to connect, especially for Bluetooth device that has no standardized services. From a terminal, we can use the  bluetoothctl tool to scan and connect with a Bluetooth device. You should make sure that the BlueZ protocol stack has been installed by running \$ apt-get install bluez Run bluetoothctl to enter the tool command window Turn the power on by running power on (Optional) You can set AutoEnable=true in /etc/bluetooth/main.conf if you want to make the Bluetooth auto power-on after reboot. Run devices to see which devices have been paired Run scan on if your desired d

### How To Use Git in Netbeans

Git is a popular version control application nowadays. Recently I have created a note about its differences with SVN and how to use it in Eclipse . There are many Git client tools. But I just want to show how to use Netbeans built-in Git tools. It makes the development process easier because it has been integrated with the IDE. Create Remote Git Repository We need a remote Git repository so everyone can store or receive any revision or updated files through the networks. We can set up our own Git server or use a public Git server like Github . In this note, I use Github. 1. Create an account in Github and create an empty Git repository Create an empty public repository in Github 2. Get the remote repository link Your Github Repository URL Create a New Project in Netbeans and Create Local Git Repository After we have a remote Git repository, we can create a project stored in the remote repository. We also need to create a local repository before we can push

### I Love Books

I like reading books since I was a kid. Thanks to my parents that let me bought any books and embraced me to read. Bookstore becomes one of my favorite places. I like to learn any topics, not only about science or IT stuffs. For me, reading a book isn't always intended to have possession in the topic, but it's for my personal pleasure and building an insight of something. some of them There're many things around us that we don't understand really well. If we try to figure it out by ourselves, we will waste most of our precious time. So, it's better to learn from the expert who has studied it well and then considering it with our common sense and logic. I grow up, many affairs had occurred, and shit happens. I realize that I have forgotten a lot of things. I likely tend to be aware of fewer things. So let me open a cupboard full of books which I've collected since a long time ago.