imagesetpixel()

(PHP 4, PHP 5, PHP 7)

画一个单一像素

说明

imagesetpixel()在$image图像中用$color颜色在$x，$y坐标（图像左上角为 0，0）上画一个点。

参见imagecreatetruecolor()和imagecolorallocate()。

This code does generate a RGB-cube (with or without borders). Because its only rendering the visible pixels its clearly fast (approx 1 up to 2 seconds). With changing the $order-variable you can see the cube from different perspectives. Entering double or tribble values (like rrg or ggg) will give you other specs of single channels. Send any sugestions to my email. 

making images with white (or close to white) background transprent 

It IS posible to "delete" pixels from an image in PHP natively - the key-function is imageAlphaBlending: 

Given an image $src and mask $mask, this applies the mask over the image, using different levels of transparency properly.

If your mask is reversed, change 127 - $mask_pix_color['alpha'] with just $mask_pix_color['alpha']

another gradient example that can do horizontal or vertical gradients 

Just a simple implementation of the Bresenham algorythm (educational purpose....)
You can find more about this and many other tutorials for gfx there: http://brand107.home.comcast.net/pc-gpe/ 

The example above diden't work, because of some errors.
This should work and it's also faster because there is only one 512*512 loop. (but it is still very slow)

--
Dino Patti

Note that you don't have to use imagecolorallocate to draw pixels. Instead, you can assign colors directly, which is much faster as well: 

imagesetpixel ($image, $x, $y, IMG_COLOR_BRUSHED);

Re: imagecreatefromtga() .. I just did some testing with what I think are valid Targa-24 and Targa-32 bit images, and modified the inner logic as follows:

The red and blue tint issue seems to be fixed by this...

here's my version of imagecreatefromtga() that's been tested to work for targa 16 .. adapted from offering by zehao dot chang at gmail dot com
function imagecreatefromtga($filename)
{
  $data = file_get_contents($filename);
 
  // Extract header information
  $string_length = fileint($data, 1, 1);
  $data_type = fileint($data, 2, 1);
  $width = fileint($data, 12, 2);
  $height = fileint($data, 14, 2);
  $bits_per_pixel = fileint($data, 16, 1);
  $bytes_per_pixel = (int) $bits_per_pixel / 8;
  
  // Currently only supporting RGB Data type
  switch ($data_type)    // Header information taken from http://astronomy.swin.edu.au/~pbourke/dataformats/tga/
  {
    case 2:   // Uncompressed RGB image
      break;
    case 0:   // No attached image data
    case 1:   // Uncompressed color-mapped image
    case 3:   // Uncompressed black and white image
    case 9:   // Runlength encoded color-mapped image
    case 10:  // Runlength encoded RGB image
    case 11:  // Compressed black and white image
    case 32:  // Compressed color-mapped data, using Huffman, Delta, and runlength encoding
    case 33:  // Compressed color-mapped data, using Huffman, Delta, and runlength encoding. 4-pass quadtree-type process
    default:
      return NULL;  // No support for any of these types
  }  
  
  // Compute things we need from the header information
  $pointer = 18 + $string_length;
  $x = 0; $y = $height - 1;
  
  $image = imagecreatetruecolor($width, $height);
  while ($pointer > 10;
      $g = ($word & 0x03E0) >> 5;
      $b = ($word & 0x001F);
      imagesetpixel($image, $x, $y, $r 

Sorry for the long intro of my function, but i just want to tell how it works and - how silly sometimes the ideas are to make such functions. Have fun ;D

Have fun ;D

@ Scott Evernden
Scott, your function works great for uncompressed TGA image files, except the results for TGA 32 with alpha don't come out right, at least in my tests. If the alpha is all white, the resulting image comes out with a red tint. If black, the resulting image has a blue tint. I don't know how to make it just ignore the alpha, but that would be handy...

This code generate a simple colortable - not a very acurate one (it would be good to define fade of color - more fading) 

I looked, but was unable to find any example code to watermark an image with a watermark that contained alpha transparency. So the following class does just that. As a parameter, it takes 2 image objects: the main image, and the watermark image (which can be a gif, png, whatever) - and optionally, an alpha setting (0-100% alpha for the watermark image). It then creates and returns a new image with the alpha-transparent watermark imposed, center-aligned, over the larger image. 

I was looking for a way to actually DELETE pixels or squares or parts of an image from an image resource, and at first I thought imagesetpixel would do the trick. Unfortunately, it merely paints over that one pixel, and as far as I knew, php didn't have any native way of deleting sections out of your image - so this little method should take care of deleting rectangular parts of your pictures!
function deleteRectangle(&$oldImage,$leftX,$leftY,$rightX,$rightY)
  {
    // Since php has no native way of delete parts of images
    // We have to divide the image into four different parts and then copy them manually to a new
    // image
    
    $xSize = imagesx($oldImage);
    $ySize = imagesy($oldImage);
    
    // Divides the image into four sections to copy
    $imagesection = array();
    $imagesection[] = array(0,0,$leftX,$ySize);
    $imagesection[] = array($leftX,0,$rightX+1,$leftY);
    $imagesection[] = array($leftX,$rightY+1,$rightX+1,$ySize);
    $imagesection[] = array($rightX+1,0,$xSize,$ySize);
    
    // Create the new, copied image
    $newImage = imagecreatetruecolor($xSize,$ySize);
    // Vital for transparency
    imagesavealpha($newImage,true);
    
    // Fills the background a transparent color
    $transparentBackground = imagecolorallocatealpha($newImage,255,255,255,127);
    imagefill($newImage,0,0,$transparentBackground);
    
    // Copies each of the four imagesections into their respective old positions
    for($i = 0;$i
An example of usage might be: 

This snippet creates a gradient images depending on the value of RGB components. Gradients allow your page to have a shadow effect. 

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