1. From this we can see that the function of the imagecreatetruecolor function is obviously to create a black background image. Its first parameter is the width of the created image, and the second parameter is the width of the created image. High, we store the return value (image identifier) of this function into a variable.
2. The function of imagecreatefromjpeg is to read the image to be divided into the memory (you may have a question here: Can't I just read it directly from the hard disk, why do I need to read it into the memory first? It's inappropriate. For example, when you usually use money, I believe you don’t put too much in your pocket. You usually take it from the bank when you need it. The same is true here. When I don’t use it in this picture, I put it on the hard drive. Inside, when the picture needs to be divided or otherwise operated, it is read into the memory. To put it bluntly, the memory provides a stage for the program to run)
3. Look at the imagecopyresampled function again. Its function is to segment the original image, and then copy it and the sample (I understand it as projection) to the background image created with imagecreatefromjpeg.
// The file
$filename = 'temp/Sunset.jpg';
$percent = 0.5;
// Content type
header('Content-type: image/jpeg');
// Get new dimensions
list($width, $height) = getimagesize($filename);
$new_width = $width * $percent;
$new_height = $height * $percent;//Create a new image using 0.5 of the length and width of the original image as the new length and width. The symbol of this image is $image_p
$image_p = imagecreatetruecolor($new_width, $new_height);
//Create a new image from a JPEG file or URL
$image = imagecreatefromjpeg($filename);
// Split the original picture starting from coordinates (100, 100). The length of the division is (400) and the height is (300) half of the original picture. Place the divided picture on the already built one starting from coordinates (0, 0). In the area
imagecopyresampled($image_p, $image, 0, 0, 100, 100, $new_width, $new_height, 400, 300);//Output
imagejpeg($image_p, null, 100); //quality is the quality of the image output ranging from 0 (worst quality, smaller file) to 100 (best quality, largest file).
?>
The above example is to divide the $image picture from the coordinates (100,100). The width after the division is 400 and the height is 300. Then the picture is projected from the coordinates (0,0) to the picture $image_p. ,,The width of the projection is $new_width, and the height is $new_height.
//File and zoom size
//$imgfile = 'smp.jpg';
//$percent = 0.2;
header('Content-type: image/jpeg');
list($width, $height) = getimagesize($imgfile);
$newwidth = $width * $percent;
$newheight = $height * $percent;
$thumb = ImageCreateTrueColor($newwidth,$newheight);
$source = imagecreatefromjpeg($imgfile);
imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
imagejpeg($thumb);
?>More detailed tutorial
/*Constructor - generate thumbnail + watermark, parameter description:
$srcFile-image file name,
$dstFile-save file name,
$markwords-watermark text,
$markimage-watermark image,
$dstW-image saving width,
$dstH-picture saving height,
$rate-image saving quality*/
makethumb("a.jpg","b.jpg","50","50");
function makethumb($srcFile,$dstFile,$dstW,$dstH,$rate=100,$markwords=null,$markimage=null)
{
$data = GetImageSize($srcFile);
switch($data[2])
{
case 1:
$im=@ImageCreateFromGIF($srcFile);
break;
case 2:
$im=@ImageCreateFromJPEG($srcFile);
break;
case 3:
$im=@ImageCreateFromPNG($srcFile);
break;
}
if(!$im) return False;
$srcW=ImageSX($im);
$srcH=ImageSY($im);
$dstX=0;
$dstY=0;
if ($srcW*$dstH>$srcH*$dstW)
{
$fdstH = round($srcH*$dstW/$srcW);
$dstY = floor(($dstH-$fdstH)/2);
$fdstW = $dstW;
}
else
{
$fdstW = round($srcW*$dstH/$srcH);
$dstX = floor(($dstW-$fdstW)/2);
$fdstH = $dstH;
}
$ni=ImageCreateTrueColor($dstW,$dstH);
$dstX=($dstX<0)?0:$dstX;
$dstY=($dstX<0)?0:$dstY;
$dstX=($dstX>($dstW/2))?floor($dstW/2):$dstX;
$dstY=($dstY>($dstH/2))?floor($dstH/s):$dstY;
$white = ImageColorAllocate($ni,255,255,255);
$black = ImageColorAllocate($ni,0,0,0);
imagefilledrectangle($ni,0,0,$dstW,$dstH,$white);//Fill background color
ImageCopyResized($ni,$im,$dstX,$dstY,0,0,$fdstW,$fdstH,$srcW,$srcH);
if($markwords!=null)
{
$markwords=iconv("gb2312","UTF-8",$markwords);
//Convert text encoding
ImageTTFText($ni,20,30,450,560,$black,"simhei.ttf",$markwords); //Write text watermark
//The parameters are in order, text size | deflection degree | abscissa | ordinate | text color | text type | text content
}
elseif($markimage!=null)
{
$wimage_data = GetImageSize($markimage);
switch($wimage_data[2])
{
case 1:
$wimage=@ImageCreateFromGIF($markimage);
break;
case 2:
$wimage=@ImageCreateFromJPEG($markimage);
break;
case 3:
$wimage=@ImageCreateFromPNG($markimage);
break;
}
imagecopy($ni,$wimage,500,560,0,0,88,31); //Write image watermark, watermark image size">The default image size is 88*31
imagedestroy($wimage);
}
ImageJpeg($ni,$dstFile,$rate);
ImageJpeg($ni,$srcFile,$rate);
imagedestroy($im);
imagedestroy($ni);
}
?>
Example 4
$thumbnail = new ImageResize();
$thumbnail->resizeimage(full path of source image, thumbnail width, thumbnail height, whether to crop (0 or 1), full path of new image);
class ImageResize {
//Image type
var $type;
//Actual width
var $width;
//Actual height
var $height;
//Changed width
var $resize_width;
//Height after change
var $resize_height;
//Whether to crop the image
var $cut;
//Source image
var $srcimg;
//Target image address
var $dstimg;
//Temporarily created image
var $im;function resizeimage($img, $wid, $hei,$c,$dstpath) {
$this->srcimg = $img;
$this->resize_width = $wid;
$this->resize_height = $hei;
$this->cut = $c;
//Type of picture
$this->type = strtolower(substr(strrchr($this->srcimg,"."),1));
//Initialize image
$this->initi_img();
//Target image address
$this -> dst_img($dstpath);
//--
$this->width = imagesx($this->im);
$this->height = imagesy($this->im);
//Generate image
$this->newimg();
ImageDestroy ($this->im);
}function newimg() {
//The proportion of the changed image
$resize_ratio = ($this->resize_width)/($this->resize_height);//Proportion of actual image
$ratio = ($this->width)/($this->height);if(($this->cut)=="1") {
//裁图 高度优先
if($ratio>=$resize_ratio){
$newimg = imagecreatetruecolor($this->resize_width,$this->resize_height);
imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width,$this->resize_height, (($this->height)*$resize_ratio), $this->height);
ImageJpeg ($newimg,$this->dstimg);
}
//裁图 宽度优先
if($ratio<$resize_ratio) {
$newimg = imagecreatetruecolor($this->resize_width,$this->resize_height);
imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, $this->resize_height, $this->width, (($this->width)/$resize_ratio));
ImageJpeg ($newimg,$this->dstimg);
}
} else {
//不裁图
if($ratio>=$resize_ratio) {
$newimg = imagecreatetruecolor($this->resize_width,($this->resize_width)/$ratio);
imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, ($this->resize_width)/$ratio, $this->width, $this->height);
ImageJpeg ($newimg,$this->dstimg);
}
if($ratio<$resize_ratio) {
$newimg = imagecreatetruecolor(($this->resize_height)*$ratio,$this->resize_height);
imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, ($this->resize_height)*$ratio, $this->resize_height, $this->width, $this->height);
ImageJpeg ($newimg,$this->dstimg);
}
}
}//初始化图象
function initi_img() {
if($this->type=="jpg") {
$this->im = imagecreatefromjpeg($this->srcimg);
}
if($this->type=="gif") {
$this->im = imagecreatefromgif($this->srcimg);
}
if($this->type=="png") {
$this->im = imagecreatefrompng($this->srcimg);
}
if($this->type=="bmp") {
$this->im = $this->imagecreatefrombmp($this->srcimg);
}
}//图象目标地址
function dst_img($dstpath) {
$full_length = strlen($this->srcimg);
$type_length = strlen($this->type);
$name_length = $full_length-$type_length;
$name = substr($this->srcimg,0,$name_length-1);
$this->dstimg = $dstpath;
//echo $this->dstimg;
}
function ConvertBMP2GD($src, $dest = false) {
if(!($src_f = fopen($src, "rb"))) {
return false;
}
if(!($dest_f = fopen($dest, "wb"))) {
return false;
}
$header = unpack("vtype/Vsize/v2reserved/Voffset", fread($src_f,14));
$info = unpack("Vsize/Vwidth/Vheight/vplanes/vbits/Vcompression/Vimagesize/Vxres/Vyres/Vncolor/Vimportant", fread($src_f, 40));
extract($info);
extract($header);
if($type != 0x4D42) { // signature "BM"
return false;
}
$palette_size = $offset - 54;
$ncolor = $palette_size / 4;
$gd_header = "";
// true-color vs. palette
$gd_header .= ($palette_size == 0) ? "xFFxFE" : "xFFxFF";
$gd_header .= pack("n2", $width, $height);
$gd_header .= ($palette_size == 0) ? "x01" : "x00";
if($palette_size) {
$gd_header .= pack("n", $ncolor);
}
// no transparency
$gd_header .= "xFFxFFxFFxFF";fwrite($dest_f, $gd_header);
if($palette_size) {
$palette = fread($src_f, $palette_size);
$gd_palette = "";
$j = 0;
while($j < $palette_size) {
$b = $palette{$j++};
$g = $palette{$j++};
$r = $palette{$j++};
$a = $palette{$j++};
$gd_palette .= "$r$g$b$a";
}
$gd_palette .= str_repeat("x00x00x00x00", 256 - $ncolor);
fwrite($dest_f, $gd_palette);
}$scan_line_size = (($bits * $width) + 7) >> 3;
$scan_line_align = ($scan_line_size & 0x03) ? 4 - ($scan_line_size &
0x03) : 0;for($i = 0, $l = $height - 1; $i < $height; $i++, $l--) {
// BMP stores scan lines starting from bottom
fseek($src_f, $offset + (($scan_line_size + $scan_line_align) * $l));
$scan_line = fread($src_f, $scan_line_size);
if($bits == 24) {
$gd_scan_line = "";
$j = 0;
while($j < $scan_line_size) {
$b = $scan_line{$j++};
$g = $scan_line{$j++};
$r = $scan_line{$j++};
$gd_scan_line .= "x00$r$g$b";
}
}
else if($bits == 8) {
$gd_scan_line = $scan_line;
}
else if($bits == 4) {
$gd_scan_line = "";
$j = 0;
while($j < $scan_line_size) {
$byte = ord($scan_line{$j++});
$p1 = chr($byte >> 4);
$p2 = chr($byte & 0x0F);
$gd_scan_line .= "$p1$p2";
}
$gd_scan_line = substr($gd_scan_line, 0, $width);
}
else if($bits == 1) {
$gd_scan_line = "";
$j = 0;
while($j < $scan_line_size) {
$byte = ord($scan_line{$j++});
$p1 = chr((int) (($byte & 0x80) != 0));
$p2 = chr((int) (($byte & 0x40) != 0));
$p3 = chr((int) (($byte & 0x20) != 0));
$p4 = chr((int) (($byte & 0x10) != 0));
$p5 = chr((int) (($byte & 0x08) != 0));
$p6 = chr((int) (($byte & 0x04) != 0));
$p7 = chr((int) (($byte & 0x02) != 0));
$p8 = chr((int) (($byte & 0x01) != 0));
$gd_scan_line .= "$p1$p2$p3$p4$p5$p6$p7$p8";
}
$gd_scan_line = substr($gd_scan_line, 0, $width);
}
fwrite($dest_f, $gd_scan_line);
}
fclose($src_f);
fclose($dest_f);
return true;
}function imagecreatefrombmp($filename) {
$tmp_name = tempnam("/tmp", "GD");
if($this->ConvertBMP2GD($filename, $tmp_name)) {
$img = imagecreatefromgd($tmp_name);
unlink($tmp_name);
return $img;
}
return false;
}
}
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