为什么输出图像文件大于使用imagick的输入？
为什么输出图像比使用imagick的输入更大？ 原jpg：http://www.persunmall.com/images/jm3.jpg
/**
* example
--------------------------------------
'jm3.jpg' => 119 k (453*680)
'l.jpg' => 275 k (400*600) // why the output jpg is much bigger than input jpg?
*/
$jy_image=new jy_image
$jy_image->output_image('jm3.jpg','l.jpg',400,0);
下面的课程：
<?php
class jy_image {
private $image = null;
private $type = null;
// 构造函数
public function __construct() {
}
// 析构函数
public function __destruct() {
if ($this->image !== null)
$this->image->destroy();
}
// 载入图像
public function open($path) {
$this->image = new Imagick($path);
if ($this->image) {
$this->type = strtolower($this->image->getImageFormat()); // jpeg
}
return $this->image;
}
public function crop($x = 0, $y = 0, $width = null, $height = null) {
if ($width == null)
$width = $this->image->getImageWidth() - $x;
if ($height == null)
$height = $this->image->getImageHeight() - $y;
if ($width <= 0 || $height <= 0)
return;
if ($this->type == 'gif') {
$image = $this->image;
$canvas = new Imagick();
$images = $image->coalesceImages();
foreach ($images as $frame) {
$img = new Imagick();
$img->readImageBlob($frame);
$img->cropImage($width, $height, $x, $y);
$canvas->addImage($img);
$canvas->setImageDelay($img->getImageDelay());
$canvas->setImagePage($width, $height, 0, 0);
}
$image->destroy();
$this->image = $canvas;
} else {
$this->image->cropImage($width, $height, $x, $y);
}
}
/*
* 更改图像大小
$fit: 适应大小方式
'force': 把图片强制变形成 $width X $height 大小
'scale': 按比例在安全框 $width X $height 内缩放图片, 输出缩放后图像大小 不完全等于 $width X $height
'scale_fill': 按比例在安全框 $width X $height 内缩放图片，安全框内没有像素的地方填充色, 使用此参数时可设置背景填充色 $bg_color = array(255,255,255)(红,绿,蓝, 透明度) 透明度(0不透明-127完全透明))
其它: 智能模能 缩放图像并载取图像的中间部分 $width X $height 像素大小
$fit = 'force','scale','scale_fill' 时： 输出完整图像
$fit = 图像方位值 时, 输出指定位置部分图像
字母与图像的对应关系如下:
north_west north north_east
west center east
south_west south south_east
*/
public function resize_to($width = 100, $height = 100, $fit = 'center', $fill_color = array(255, 255, 255, 0)) {
// 保证其中一边，另外一边相应缩放
if($width==0 || $height==0){
$image = $this->image;
$src_width = $image->getImageWidth();
$src_height = $image->getImageHeight();
if($width>0 && $height==0){
$width=($width>$src_width)?$src_width:$width;
$height = $src_height*($width/$src_width);
}
else if($width==0 && $height>0){
$height=($height>$src_height)?$src_height:$height;
$width = $src_width*($height/$src_height);
}
$fit='force';
}
switch ($fit) {
case 'force': // 强制缩放，会变形
if ($this->type == 'gif') {
$image = $this->image;
$canvas = new Imagick();
$images = $image->coalesceImages();
foreach ($images as $frame) {
$img = new Imagick();
$img->readImageBlob($frame);
$img->thumbnailImage($width, $height, false);
$canvas->addImage($img);
$canvas->setImageDelay($img->getImageDelay());
}
$image->destroy();
$this->image = $canvas;
} else {
$this->image->thumbnailImage($width, $height, false);
}
break;
case 'scale':
if ($this->type == 'gif') {
$image = $this->image;
$images = $image->coalesceImages();
$canvas = new Imagick();
foreach ($images as $frame) {
$img = new Imagick();
$img->readImageBlob($frame);
$img->thumbnailImage($width, $height, true);
$canvas->addImage($img);
$canvas->setImageDelay($img->getImageDelay());
}
$image->destroy();
$this->image = $canvas;
} else {
$this->image->thumbnailImage($width, $height, true);
}
break;
case 'scale_fill': // 填充白色
$size = $this->image->getImagePage();
$src_width = $size['width'];
$src_height = $size['height'];
$x = 0;
$y = 0;
$dst_width = $width;
$dst_height = $height;
if ($src_width * $height > $src_height * $width) {
$dst_height = intval($width * $src_height / $src_width);
$y = intval(($height - $dst_height) / 2);
} else {
$dst_width = intval($height * $src_width / $src_height);
$x = intval(($width - $dst_width) / 2);
}
$image = $this->image;
$canvas = new Imagick();
$color = 'rgba(' . $fill_color[0] . ',' . $fill_color[1] . ',' . $fill_color[2] . ',' . $fill_color[3] . ')';
if ($this->type == 'gif') {
$images = $image->coalesceImages();
foreach ($images as $frame) {
$frame->thumbnailImage($width, $height, true);
$draw = new ImagickDraw();
$draw->composite($frame->getImageCompose(), $x, $y, $dst_width, $dst_height, $frame);
$img = new Imagick();
$img->newImage($width, $height, $color, 'gif');
$img->drawImage($draw);
$canvas->addImage($img);
$canvas->setImageDelay($img->getImageDelay());
$canvas->setImagePage($width, $height, 0, 0);
}
} else {
$image->thumbnailImage($width, $height, true);
$draw = new ImagickDraw();
$draw->composite($image->getImageCompose(), $x, $y, $dst_width, $dst_height, $image);
$canvas->newImage($width, $height, $color, $this->get_type());
$canvas->drawImage($draw);
$canvas->setImagePage($width, $height, 0, 0);
}
$image->destroy();
$this->image = $canvas;
break;
default:
$size = $this->image->getImagePage();
$src_width = $size['width'];
$src_height = $size['height'];
$crop_x = 0;
$crop_y = 0;
$crop_w = $src_width;
$crop_h = $src_height;
if ($src_width * $height > $src_height * $width) {
$crop_w = intval($src_height * $width / $height); // 100*50 =>50*100 输出：25*50
} else {
$crop_h = intval($src_width * $height / $width); //50*100 =>100*50 输出：50*25
}
switch ($fit) {
case 'north_west':
$crop_x = 0;
$crop_y = 0;
break;
case 'north':
$crop_x = intval(($src_width - $crop_w) / 2);
$crop_y = 0;
break;
case 'north_east':
$crop_x = $src_width - $crop_w;
$crop_y = 0;
break;
case 'west':
$crop_x = 0;
$crop_y = intval(($src_height - $crop_h) / 2);
break;
case 'center':
$crop_x = intval(($src_width - $crop_w) / 2);
$crop_y = intval(($src_height - $crop_h) / 2);
break;
case 'east':
$crop_x = $src_width - $crop_w;
$crop_y = intval(($src_height - $crop_h) / 2);
break;
case 'south_west':
$crop_x = 0;
$crop_y = $src_height - $crop_h;
break;
case 'south':
$crop_x = intval(($src_width - $crop_w) / 2);
$crop_y = $src_height - $crop_h;
break;
case 'south_east':
$crop_x = $src_width - $crop_w;
$crop_y = $src_height - $crop_h;
break;
default:
$crop_x = intval(($src_width - $crop_w) / 2);
$crop_y = intval(($src_height - $crop_h) / 2);
}
$image = $this->image;
$canvas = new Imagick();
if ($this->type == 'gif') {
$images = $image->coalesceImages();
foreach ($images as $frame) {
$img = new Imagick();
$img->readImageBlob($frame);
$img->cropImage($crop_w, $crop_h, $crop_x, $crop_y);
$img->thumbnailImage($width, $height, true);
$canvas->addImage($img);
$canvas->setImageDelay($img->getImageDelay());
$canvas->setImagePage($width, $height, 0, 0);
}
} else {
$image->cropImage($crop_w, $crop_h, $crop_x, $crop_y);
$image->thumbnailImage($width, $height, true);
$canvas->addImage($image);
$canvas->setImagePage($width, $height, 0, 0);
}
$image->destroy();
$this->image = $canvas;
}
}
// 添加水印图片
public function add_watermark($path, $x = 0, $y = 0) {
$watermark = new Imagick($path);
// 默认水印位置 by jimmy 2014-4-11
if(empty($x) && empty($y)){
$im_w= $this->image->getImageWidth();
$im_h = $this->image->getImageHeight();
$wa_w = $watermark->getImageWidth();
$wa_h = $watermark->getImageHeight();
$x=($im_w-$wa_w)/2;
$y=($im_h-$wa_h-50);
}
$draw = new ImagickDraw();
$draw->composite($watermark->getImageCompose(), $x, $y, $watermark->getImageWidth(), $watermark->getimageheight(), $watermark);
if ($this->type == 'gif') {
$image = $this->image;
$canvas = new Imagick();
$images = $image->coalesceImages();
foreach ($image as $frame) {
$img = new Imagick();
$img->readImageBlob($frame);
$img->drawImage($draw);
$canvas->addImage($img);
$canvas->setImageDelay($img->getImageDelay());
}
$image->destroy();
$this->image = $canvas;
} else {
$this->image->drawImage($draw);
}
}
// 添加水印文字
public function add_text($text, $x = 0, $y = 0, $angle = 0, $style = array()) {
$draw = new ImagickDraw();
if (isset($style['font']))
$draw->setFont($style['font']);
if (isset($style['font_size']))
$draw->setFontSize($style['font_size']);
if (isset($style['fill_color']))
$draw->setFillColor($style['fill_color']);
if (isset($style['under_color']))
$draw->setTextUnderColor($style['under_color']);
if ($this->type == 'gif') {
foreach ($this->image as $frame) {
$frame->annotateImage($draw, $x, $y, $angle, $text);
}
} else {
$this->image->annotateImage($draw, $x, $y, $angle, $text);
}
}
// 保存到指定路径
public function save_to($path) {
$this->image->stripImage();
if ($this->type == 'gif') {
$this->image->writeImages($path, true);
} else {
$this->image->writeImage($path);
}
}
// 输出图像
public function output($header = true) {
if ($header)
header('Content-type: ' . $this->type);
echo $this->image->getImagesBlob();
}
public function get_width() {
$size = $this->image->getImagePage();
return $size['width'];
}
public function get_height() {
$size = $this->image->getImagePage();
return $size['height'];
}
// 设置图像类型， 默认与源类型一致
public function set_type($type = 'png') {
$this->type = $type;
$this->image->setImageFormat($type);
}
// 获取源图像类型
public function get_type() {
return $this->type;
}
// 当前对象是否为图片
public function is_image() {
if ($this->image)
return true;
else
return false;
}
public function thumbnail($width = 100, $height = 100, $fit = true) {
$this->image->thumbnailImage($width, $height, $fit);
} // 生成缩略图 $fit为真时将保持比例并在安全框 $width X $height 内生成缩略图片
/*
添加一个边框
$width: 左右边框宽度
$height: 上下边框宽度
$color: 颜色: RGB 颜色 'rgb(255,0,0)' 或 16进制颜色 '#FF0000' 或颜色单词 'white'/'red'...
*/
public function border($width, $height, $color = 'rgb(220, 220, 220)') {
$color = new ImagickPixel();
$color->setColor($color);
$this->image->borderImage($color, $width, $height);
}
public function blur($radius, $sigma) {
$this->image->blurImage($radius, $sigma);
} // 模糊
public function gaussian_blur($radius, $sigma) {
$this->image->gaussianBlurImage($radius, $sigma);
} // 高斯模糊
public function motion_blur($radius, $sigma, $angle) {
$this->image->motionBlurImage($radius, $sigma, $angle);
} // 运动模糊
public function radial_blur($radius) {
$this->image->radialBlurImage($radius);
} // 径向模糊
public function add_noise($type = null) {
$this->image->addNoiseImage($type == null ? imagick::NOISE_IMPULSE : $type);
} // 添加噪点
public function level($black_point, $gamma, $white_point) {
$this->image->levelImage($black_point, $gamma, $white_point);
} // 调整色阶
public function modulate($brightness, $saturation, $hue) {
$this->image->modulateImage($brightness, $saturation, $hue);
} // 调整亮度、饱和度、色调
public function charcoal($radius, $sigma) {
$this->image->charcoalImage($radius, $sigma);
} // 素描
public function oil_paint($radius) {
$this->image->oilPaintImage($radius);
} // 油画效果
public function flop() {
$this->image->flopImage();
} // 水平翻转
public function flip() {
$this->image->flipImage();
} // 垂直翻转
/**
* 压缩图片 by jimmy 2014-4-11
* ----------------------------------------
*/
function compress($quality=100){
$this->image->setImageFormat('JPEG');
$this->image->setImageCompression(Imagick::COMPRESSION_JPEG);
$q = $this->image->getImageCompressionQuality();
$q = $q* $quality/100;
if($q==0){
$q = $quality;
}
$this->image->setImageCompressionQuality($q);
$this->image->stripImage();
}
/**
* 综合各个步骤输出 by jimmy 2014-4-11
* ----------------------------------------
*/
function output_image($srcFile,$destFile,$w=0,$h=0,$quality=100,$waterFile='',$fit="scale_fill"){
$this->open($srcFile);
$this->compress($quality);
if(!empty($waterFile)){
$this->add_watermark($waterFile);
}
if($w+$h>0){
$this->resize_to($w,$h,$fit);
}
$this->save_to($destFile);
}
}
1 个答案:
答案 0 :(得分：1)
首先，从你的评论＆＃34;甚至质量= 80，l.jpg比jm3.jpg更大＃34;我认为这是错误的。以较低质量重新保存文件会产生以下结果。
119,300 = original image
266,008 = Resized at 100%
245,145 = Resized at 100% + despeckle
97,536 = Resized at 90% quality
88,342 = Resized at 90% quality with despeckle
我还添加了Imagick::despeckle，因为调整大小会引入斑点。
然而，你要问的基本问题＆＃34;为什么重新保存JPEG图像会增加文件大小，质量相同？＆＃34;
简单的答案是，因为它是一种有损格式，在将图像保存为JPEG后，新图像中可能会有更多信息。为了以相同的质量保存图像，需要对附加信息进行编码，这会占用额外的空间。
考虑一个简单的正弦波;它包含的信息非常少。然后想象我们将其保存为图像＆＃39;具有有损格式，可以修剪正弦波的末端，例如：
无论您考虑新形状的哪种方式，它都需要编码以保留新形状的更多信息，因此以100％质量重新保存它会占用原始有损保存图像的更多空间。
以较低的质量重新保存会产生较小的图像，但会迅速丢失图像中的信息，因为每次保存都是近似值的近似值。
TL：DR将PNG用于所有中间格式，并仅使用JPG作为客户的最终输出。
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