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    Image Processing and GD

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    User Contributed Notes 7 notes

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    7
    kurdtpage at gmail dot com
    13 years ago
    When using GD, please make sure of the following things:

    1. The file that is used to manipulate images is saved as ANSI format and not UTF-8
    2. There is no space in front of the opening tag <?php
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    6
    mail at ecross dot nl
    14 years ago
    hello there,
    i made a function to create a gradient image.

    description:
    gradient(int image_width, int image_height,
    int start_red, int start_green, int start_blue,
    int end_red, int end_green, int end_blue,
    bool vertical)

    function:
    <?php
    function gradient($image_width, $image_height,$c1_r, $c1_g, $c1_b, $c2_r, $c2_g, $c2_b, $vertical=false)
    {
    // first: lets type cast;
    $image_width = (integer)$image_width;
    $image_height = (integer)$image_height;
    $c1_r = (integer)$c1_r;
    $c1_g = (integer)$c1_g;
    $c1_b = (integer)$c1_b;
    $c2_r = (integer)$c2_r;
    $c2_g = (integer)$c2_g;
    $c2_b = (integer)$c2_b;
    $vertical = (bool)$vertical;

    // create a image
    $image  = imagecreatetruecolor($image_width, $image_height);

    // make the gradient
    for($i=0; $i<$image_height; $i++)
    {
    $color_r = floor($i * ($c2_r-$c1_r) / $image_height)+$c1_r;
    $color_g = floor($i * ($c2_g-$c1_g) / $image_height)+$c1_g;
    $color_b = floor($i * ($c2_b-$c1_b) / $image_height)+$c1_b;

    $color = ImageColorAllocate($image, $color_r, $color_g, $color_b);
    imageline($image, 0, $i, $image_width, $i, $color);
    }

    # Prints out all the figures and picture and frees memory
    header('Content-type: image/png');

    if(    $vertical){$image = imagerotate($image, 90, 0);}
    ImagePNG($image);
    imagedestroy($image);
    }
    ?>
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    5
    herbert dot walde at googlemail dot com
    12 years ago
    In case your script is using output-buffering-functions somewhere, then you have to clear the buffer first ( with ob_clear() ), before outputting an image with a function like imagepng().

    And you should make sure that no buffer will get send after outputing an image by using the ob_end_flush()-function.

    Furthermore you should check if a buffer has already been flushed somewhere before. This can be done using the headers_sent()-function.

    Here is the full solution:

    <?php
    if(headers_sent()){
        die(    'Headers have been send somewhere within my script');
    }

    ob_clean(); //Clears the buffer

    header('Content-type: image/png');
    imagepng($img, NULL, 0,  NULL);

    ob_end_flush(); //Now we send the header and image plus we make sure that nothing will get send from now on (including possible shutdown-functions and __destruct()-methods) till the end of page-execution
    ?>
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    3
    Thomas
    15 years ago
    You know, maybe this goes without saying, but I thought I would drop a note in here.  When developing code to resize images, it is best not to use GD.  When using the current GD methodologies, you are reading content from an image and manipulating it.  By then writing that content to a brand new file, you are losing the EXIF data.

    For purposes when you want to retain EXIF data, it is recommended that you compile in and use the PECL Imagick extension.  It has great resizing methods built right in and the EXIF data is retained.
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    0
    code at ashleyhunt dot co dot uk
    16 years ago
    I have been looking to send the output from GD to a text string without proxying via a file or to a browser.

    I have come up with a solution.

    This code buffers the output between the ob_start() and ob_end() functions into ob_get_contents()

    See the example below

    <?php
    // Create a test source image for this example
    $im = imagecreatetruecolor(300, 50);
    $text_color = imagecolorallocate($im, 233, 14, 91);
    imagestring($im, 1, 5, 5,  'A Simple Text String', $text_color);

    // start buffering
    ob_start();
    // output jpeg (or any other chosen) format & quality
    imagejpeg($im, NULL, 85);
    // capture output to string
    $contents = ob_get_contents();
    // end capture
    ob_end_clean();

    // be tidy; free up memory
    imagedestroy($im);

    // lastly (for the example) we are writing the string to a file
    $fh = fopen("./temp/img.jpg", "a+" );
            fwrite( $fh, $contents );
    fclose( $fh );
    ?>

    Enjoy!
    Ashley
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    -3
    mhkh1366 at gmail dot com
    5 years ago
    ### Attention:
    For previewing images created by GD library in php file format in web browser, you should attention these two items:
    1_ Make sure that GD is enable in php.ini
    2_ Make sure that your php file encoding is ANSI/ASCII or you should use ob_clean() function before changing the header by header() function
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    -6
    donatj at gmail dot com
    13 years ago
    UTF-8 is fine with GD - as well as any other Unicode transformation format - you just need to ensure your saved file doesn't contain the dreaded byte order mark.
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