生成图像缩略图(支持:JPEG,GIT,PNG,BMP)
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2022-04-15 10:10:58
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<?php class Thumb { public function create($srcPath, $dstPath, $dstWidth, $dstHeight) { if (!file_exists($srcPath)) { return false; } @$srcSize = getimagesize($srcPath); if (empty($srcSize)) { return false; } $srcWith = intval($srcSize[0]); $srcHeight = intval($srcSize[1]); //如果原始图片的尺寸大于指定缩略图的尺寸,则生成缩略图,否则拷贝原始文件 if ($srcWith <= $dstWidth && $srcHeight <= $dstHeight) { return copy($srcPath, $dstPath); } //读取原始图片资源 @$srcImage = imagecreatefromjpeg($srcPath); if (empty($srcImage)) { @$srcImage = imagecreatefromgif($srcPath); } if (empty($srcImage)) { @$srcImage = imagecreatefrompng($srcPath); } if (empty($srcImage)) { @$srcImage = $this->_imageCreateFromBMP($srcPath); } if (empty($srcImage)) { return false; } //获取缩略图的尺寸,并据此生成新的图像 $dstSize = $this->_getDstSize( $srcWith, $srcHeight, $dstWidth, $dstHeight ); @$dstImage = imagecreatetruecolor( $dstSize['width'], $dstSize['height'] ); @imagecopyresampled( $dstImage, $srcImage , 0, 0, 0, 0, $dstSize['width'], $dstSize['height'], $srcWith, $srcHeight ); return @imagepng($srcPath, $dstPath); } private function _imageCreateFromBMP($filePath) { $fileHandle = fopen($filePath, 'rb'); if (empty($fileHandle)) { return false; } $file = unpack( 'vfile_type/Vfile_size/Vreserved/Vbitmap_offset', fread($fileHandle, 14) ); if ($file['file_type'] != 19778) { return false; } $bmp = unpack( 'Vheader_size/Vwidth/Vheight/vplanes/'. 'vbits_per_pixel/Vcompression/Vsize_bitmap/'. 'Vhoriz_resolution/Vvert_resolution/Vcolors_used/Vcolors_important', fread($fileHandle, 40) ); $bmp['colors'] = pow(2, $bmp['bits_per_pixel']); if ($bmp['size_bitmap'] == 0) { $bmp['size_bitmap'] = $file['file_size'] - $file['bitmap_offset']; } $bmp['bytes_per_pixel'] = $bmp['bits_per_pixel'] / 8; $bmp['bytes_per_pixel2'] = ceil($bmp['bytes_per_pixel']); $bmp['decal'] = $bmp['width'] * $bmp['bytes_per_pixel'] / 4; $bmp['decal'] -= floor($bmp['width'] * $bmp['bytes_per_pixel'] / 4); $bmp['decal'] = 4 - (4 * $bmp['decal']); if ($bmp['decal'] == 4) { $bmp['decal'] = 0; } $palette = array(); if ($bmp['colors'] < 16777216) { $palette = unpack( 'V' . $bmp['colors'], fread($fileHandle, $bmp['colors'] * 4) ); } $image = fread($fileHandle, $bmp['size_bitmap']); $vide = chr(0); $res = imagecreatetruecolor($bmp['width'], $bmp['height']); $p = 0; $y = $bmp['height'] - 1; while ($y >= 0) { $x = 0; while ($x < $bmp['width']) { if ($bmp['bits_per_pixel'] == 24) { $color = unpack('V', substr($image, $p, 3) . $vide); } else if ($bmp['bits_per_pixel'] == 16) { $color = unpack('n', substr($image, $p, 2)); $color[1] = $palette[$color[1]+1]; } else if ($bmp['bits_per_pixel'] == 8) { $color = unpack('n', $vide . substr ($image, $p, 1)); $color[1] = $palette[$color[1]+1]; } else if ($bmp['bits_per_pixel'] ==4) { $color = unpack('n', $vide . substr($image, floor($p), 1)); if (($p * 2) % 2 == 0) { $color[1] = ($color[1] >> 4); } else { $color[1] = ($color[1] & 0x0F); } $color[1] = $palette[$color[1] + 1]; } else if ($bmp['bits_per_pixel'] == 1) { $color = unpack('n', $vide . substr($image, floor($p), 1)); switch (($p * 8) % 8) { case 0: $color[1] = ($color[1] >> 7); break; case 1: $color[1] = ($color[1] & 0x40) >> 6; break; case 2: $color[1] = ($color[1] & 0x20) >> 5; break; case 3: $color[1] = ($color[1] & 0x10) >> 4; break; case 4: $color[1] = ($color[1] & 0x8) >> 3; break; case 5: $color[1] = ($color[1] & 0x4) >> 2; break; case 6: $color[1] = ($color[1] & 0x2) >> 1; break; case 7: $color[1] = ($color[1] & 0x1); break; } $color[1] = $palette[$color[1] + 1]; } else { return false; } imagesetpixel($res, $x, $y, $color[1]); $x++; $p += $bmp['bytes_per_pixel']; } $y--; $p += $bmp['decal']; } fclose($fileHandle); return $res; } private function _getDstSize($srcWith, $srcHeight, $dstWidth, $dstHeight) { $size = array('width' => $srcWith, 'height' => $srcHeight); if ($dstWidth > 0 && $dstHeight > 0) { if ($srcWith > 0 && $srcHeight > 0) { if ($srcWith / $srcHeight >= $dstWidth / $dstHeight) { if ($srcWith > $dstWidth) { $size['width'] = $dstWidth; $size['height'] = $srcHeight * $dstWidth / $srcWith; } } else { if ($srcHeight > $dstHeight) { $size['width'] = $srcWith * $dstHeight / $srcHeight; $size['height'] = $dstHeight; } } } } return $size; } }