May
14

Check if file or folder exists in C#

George Karpouzas C# Add you comment

To find out if a file exists or not, use:

if(System.IO.File.Exists(path)) { ... }

for a folder, use:

if(System.IO.Directory.Exists(path)) { ... }
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May
08

Base64 Encoding and Decoding in C#

George Karpouzas C# Add you comment

Encoding string to Base64 format:

public String Encode2Base64(String text)
{
	try
	{
		return Convert.ToBase64String(ASCIIEncoding.ASCII.GetBytes(text));
	}
	catch (Exception)
	{
		return null;
	}
}

Decoding string from Base64 format:

public String DecodefromBase64(String text)
{
	try
	{
		return Encoding.ASCII.GetString(Convert.FromBase64String(text));
	}
	catch (Exception)
	{
		return null;
	}
}
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May
06

Using MySQL Prepared Statements in PHP

George Karpouzas MySQL, PHP Add you comment

A good reason to use prepared statements is to avoid SQL injection without needing to escape data.

Connect

$conn = mysqli_connect("localhost", "user_name", "xxxxxxxx", "dbname");
if ($conn->connect_errno) {
    echo "Connection failed: " . $conn->connect_errno . " - " . $conn->connect_error;
}

New statement

$stmt = $conn->stmt_init();

Execute Prepared Statement

if($stmt->prepare("INSERT INTO `users` (`Username`, `Password`, `Salt`) VALUES (?, ?, ?)")) {
	$stmt->bind_param('sss', $username, $passwd, $salt); //sss -> string string string
	$username = 'JohnDoe';
	$passwd = '3g435g245g45g54h3455h544h2';
	$salt = 'h45534h634GWgewgESgwEgseagGSAEGg4634h634h';
	$stmt->execute();
	$stmt->close();
}
else{
	echo "Prepare failed: " . $conn->errno . " " . $conn->error;
}

Data types – bind_param

i – integer
d – double
s – string
b – blob – binary

Disconnect

$conn->close();
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May
04

Drupal 7 default regions

George Karpouzas Drupal Add you comment

Default regions for Drupal 7

regions[header] = Header
regions[highlighted] = Highlighted
regions[help] = Help
regions[content] = Content
regions[sidebar_first] = Left sidebar
regions[sidebar_second] = Right sidebar
regions[footer] = Footer

You can override the values for your specific needs by editing your theme’s info file.

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May
02

Reset Drupal’s theme using MySQL

George Karpouzas Drupal, MySQL Add you comment

If you have broken everything by renaming, editing or removing the default theme and you have trouble signing in to administration panel then in this case you can fix the problem by changing Drupal’s default theme in MySQL database. Open PHPMyAdmin or MySQL Workbench and execute the following sql queries.

Set Garland theme as default:

UPDATE system SET STATUS=1 WHERE name = 'garland';

 
Change the variable theme_default value:

UPDATE variable SET VALUE='s:7:"garland"' WHERE name = 'theme_default';

 
Clear cache:

TRUNCATE cache;

 

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Apr
26

Create JSON data in Java

George Karpouzas Java Add you comment

1. Download json-simple library (.jar file) from here.

2. Add a reference to the json-simple jar file.

3. Import package org.json.simple.JSONObject

4. Write your code:

JSONObject jsonobj = new JSONObject();
jsonobj.put("city", "Athens");
jsonobj.put("country", "Greece");
System.out.println(jsonobj.toString());
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Apr
18

Convert Text into Image with C#

George Karpouzas C# Add you comment

Let’s see how we can convert text into an image using C#:

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public Image DrawText(String text)
{
	Image img = new Bitmap(64, 64);
	Graphics drawing = Graphics.FromImage(img);
	drawing.Clear(Color.Yellow);
	Brush textBrush = new SolidBrush(Color.Black);
	drawing.DrawString(text, new Font(new FontFamily("Trebuchet MS"), 12f), textBrush, 0, 0);
	drawing.Save();
	textBrush.Dispose();
	drawing.Dispose();
	return img;
}
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Apr
16

Get Image File Type from magic numbers

manager Java Add you comment

Magic numbers are the first bits of a file which uniquely identify the type of the file.

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public class FileIdentifier {
    private final int BMP = 0x424d;
    private final int GIF = 0x47494638;
    private final int JPEG = 0xffd8ffe0;
    private final int PNG = 0x89504e47;
 
    /**
     * get image file type based on file first bytes - magic number
     * @param filename
     * @return format name
     */
    public String getImageFileType(String filename) {
        try {
            try (DataInputStream input = new DataInputStream(
                         new BufferedInputStream(
                         new FileInputStream(filename)))) {
                for (int i = 0; i < 1; i++){
                    switch(input.readInt()){
                        case BMP:
                            return "bitmap";
                        case GIF:
                            return "gif";
                        case JPEG:
                            return "jpeg";
                        case PNG:
                            return "png";
                        default:
                            return "Unknown format";
                    }
                }
                return "Unknown format";
            }
        } catch (IOException ex) {
            System.err.println(ex.getMessage());
            return "Unknown format";
        }
    }
}
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Apr
14

Convert array of bytes into image in Java SE

George Karpouzas Java Add you comment

First we are going to detect the mimetype from bytes array and then save the bytes into an image file.

 

    /**
     * Save bytes array to image file
     * @param chunk 
     */
    public void Bytes2Image( byte[] chunk, String filename, String folder) {
        if(folder.charAt(folder.length()-1) != '/') folder += "/";
        BufferedImage image;
        String formatName = "jpg";
        try {
            ImageInputStream iis = ImageIO.createImageInputStream(new ByteArrayInputStream(chunk));
            Iterator<ImageReader> iter=ImageIO.getImageReaders(iis);
            if (iter.hasNext()) {
                ImageReader reader = (ImageReader)iter.next();
                reader.setInput(iis);
                formatName = reader.getFormatName();
            }
            image = ImageIO.read( new ByteArrayInputStream( chunk ) );
            ImageIO.write(image, formatName, new File(folder+filename+"."+formatName.toLowerCase()));
        } catch (IOException ex) {
            System.err.println(ex.getMessage());
        }
    }

Example

Bytes2Image(myimagebytes, "my_image_file", "/path/to/images");
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Apr
13

Create QR codes with c

George Karpouzas C, Linux Add you comment

Library

To create QR codes we are going to use open source library libqrencode.

Installation

I you are in Ubuntu install libqrencode by issuing the following command:

sudo apt-get install libqrencode libqrencode-dev

Source code

#include <stdio.h>
#include <qrencode.h>
#include <errno.h>
 
int main(){
    QRcode *qrcode;
    qrcode = QRcode_encodeString("http://webnetsoft.gr", 4, QR_ECLEVEL_H, QR_MODE_8, 0);
 
    if(qrcode == NULL) {
	printf("An error has occured (%d).\n", errno);
	if(errno == EINVAL){
		printf("Invalid input object\n");
	}
	else if(errno == ENOMEM) {
		printf("Unable to allocate memory for input objects.\n");
	}
	else if(errno == ERANGE) {
		printf("Input data is too large.\n");
	}
	return 1;
    }
 
    printf("%s", qrcode->data);
    QRcode_free(qrcode);
    return 0;
}

Compile

gcc -o encode encode.c -lqrencode
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