imagetypes
In the previous note by -> lukeross at sys3175 dot co dot uk <- there is a coding error in the for() loops. After correcting the error, I found that this function did a great job of converting color images to 2 colors.
The following is the corrected function code:
function ImageColorFloydSteinberg($dst_img, $src_img) {
ImageColorAllocate($dst_img, 0,0,0);
ImageColorAllocate($dst_img, 255,255,255);
$isx = ImageSX($src_img);
$isy = ImageSY($src_img);
$grey_img = ImageCreate($isx, $isy);
for ($a = 0; $a <= 255; $a++) ImageColorAllocate($grey_img, $a,$a,$a);
$isx -= 1; // To correct pixel count in source image width starting from 0
$isy -= 1; // Correcting pixel count in source image height starting from 0
for($x = 0; $x <= $isx; $x++) {
for($y = 0; $y <= $isy; $y++) {
$color = ImageColorsForIndex($src_img, ImageColorAt($src_img, $x, $y));
$greyscale = .299 * $color["red"] + .587 * $color["green"] + .114 * $color["blue"];
ImageSetPixel($grey_img, $x, $y, ImageColorClosest($grey_img, $greyscale, $greyscale, $greyscale));
}
}
for($x = 0; $x <= $isx; $x++) {
for($y = 0; $y <= $isy; $y++) {
$color = ImageColorsForIndex($grey_img, ImageColorAt($grey_img, $x, $y));
if ($color["red"] > 128) {
ImageSetPixel($dst_img, $x, $y, ImageColorClosest($dst_img,255,255,255));
$err = $color["red"] - 255;
} else {
ImageSetPixel($dst_img, $x, $y, ImageColorClosest($dst_img,0,0,0));
$err = $color["red"];
}
if ($x != $isx) {
$color2 = ImageColorsForIndex($grey_img, ImageColorAt($grey_img, $x+1, $y));
$newgrey = $color2["red"] + $err * 7 / 16;
ImageSetPixel($grey_img, $x+1, $y, ImageColorClosest($grey_img,$newgrey, $newgrey, $newgrey));
}
if ($x != 0) {
$color2 = ImageColorsForIndex($grey_img, ImageColorAt($grey_img, $x-1, $y));
$newgrey = $color2["red"] + $err * 3 / 16;
ImageSetPixel($grey_img, $x-1, $y, ImageColorClosest($grey_img,$newgrey, $newgrey, $newgrey));
}
if ($y != $isy) {
$color2 = ImageColorsForIndex($grey_img, ImageColorAt($grey_img, $x, $y+1));
$newgrey = $color2["red"] + $err * 5 / 16;
ImageSetPixel($grey_img, $x, $y+1, ImageColorClosest($grey_img,$newgrey, $newgrey, $newgrey));
}
if ($x != $isx && $y != $isy) {
$color2 = ImageColorsForIndex($grey_img, ImageColorAt($grey_img, $x+1, $y+1));
$newgrey = $color2["red"] + $err / 16;
ImageSetPixel($grey_img, $x+1, $y+1, ImageColorClosest($grey_img,$newgrey, $newgrey, $newgrey));
}
}
}
imagedestroy($grey_img);
}
imagewbmp
(PHP 4 >= 4.0.1, PHP 5)
imagewbmp — Output image to browser or file
설명
bool imagewbmp
( resource $image
[, string $filename
[, int $foreground
]] )
imagewbmp() outputs or save a WBMP version of the given image.
인수
- image
-
imagecreatetruecolor() 등의 이미지 생성 함수에서 반환한 이미지 자원.
- filename
-
The path to save the file to. If not set or NULL, the raw image stream will be outputted directly.
- foreground
-
You can set the foreground color with this parameter by setting an identifier obtained from imagecolorallocate(). The default foreground color is black.
반환값
성공할 경우 TRUE를, 실패할 경우 FALSE를 반환합니다.
예제
Example #1 Outputting a WBMP image
<?php
// Create a blank image and add some text
$im = imagecreatetruecolor(120, 20);
$text_color = imagecolorallocate($im, 233, 14, 91);
imagestring($im, 1, 5, 5, 'A Simple Text String', $text_color);
// Set the content type header - in this case image/vnd.wap.wbmp
// Hint: see image_type_to_mime_type() for content-types
header('Content-Type: image/vnd.wap.wbmp');
// Output the image
imagewbmp($im);
// Free up memory
imagedestroy($im);
?>
Example #2 Saving the WBMP image
<?php
// Create a blank image and add some text
$im = imagecreatetruecolor(120, 20);
$text_color = imagecolorallocate($im, 233, 14, 91);
imagestring($im, 1, 5, 5, 'A Simple Text String', $text_color);
// Save the image
imagewbmp($im, 'simpletext.wbmp');
// Free up memory
imagedestroy($im);
?>
Example #3 Outputting the image with a different foreground
<?php
// Create a blank image and add some text
$im = imagecreatetruecolor(120, 20);
$text_color = imagecolorallocate($im, 233, 14, 91);
imagestring($im, 1, 5, 5, 'A Simple Text String', $text_color);
// Set the content type header - in this case image/vnd.wap.wbmp
// Hint: see image_type_to_mime_type() for content-types
header('Content-Type: image/vnd.wap.wbmp');
// Set a replacement foreground color
$foreground_color = imagecolorallocate($im, 255, 0, 0);
imagewbmp($im, NULL, $foreground_color);
// Free up memory
imagedestroy($im);
?>
주의
Note:
WBMP support is only available if PHP was compiled against GD-1.8 or later.
참고
- image2wbmp() - Output image to browser or file
- imagepng() - Output a PNG image to either the browser or a file
- imagegif() - Output image to browser or file
- imagejpeg() - Output image to browser or file
- imagetypes() - Return the image types supported by this PHP build
add a note
User Contributed Notes
imagewbmp
andre at bynetworld dot com
19-Dec-2007 05:31
lukeross at sys3175 dot co dot uk
28-Feb-2002 01:57
As has been commented before, GD doesnt do a very good translation to 2-colours, especially for photos. The following routine converts to two colours, I believe using error diffusion (the algorithm's nicked off news). It's slow, but just about adequate for small images and low load. I suspect it can be made much more efficient :-)
function ImageColorFloydSteinberg($dst_img, $src_img) {
ImageColorAllocate($dst_img, 0,0,0);
ImageColorAllocate($dst_img, 255,255,255);
$grey_img = ImageCreate(ImageSX($src_img), ImageSY($src_img));
for ($a = 0; $a <= 255; $a++) ImageColorAllocate($grey_img, $a,$a,$a);
for($x = 0; $x <= ImageSX($src_img); $x++) {
for($y = 0; $y <= ImageSY($src_img); $y++) {
$color = ImageColorsForIndex($src_img, ImageColorAt($src_img, $x, $y));
$greyscale = .299 * $color["red"] + .587 * $color["green"] + .114 * $color["blue"];
ImageSetPixel($grey_img, $x, $y, ImageColorClosest($grey_img, $greyscale, $greyscale, $greyscale));
}
}
for($x = 0; $x <= ImageSX($src_img); $x++) {
for($y = 0; $y <= ImageSY($src_img); $y++) {
$color = ImageColorsForIndex($grey_img, ImageColorAt($grey_img, $x, $y));
if ($color["red"] > 128) {
ImageSetPixel($dst_img, $x, $y, ImageColorClosest($dst_img,255,255,255));
$err = $color["red"] - 255;
} else {
ImageSetPixel($dst_img, $x, $y, ImageColorClosest($dst_img,0,0,0));
$err = $color["red"];
}
if ($x != ImageSx($src_img)) {
$color2 = ImageColorsForIndex($grey_img, ImageColorAt($grey_img, $x+1, $y));
$newgrey = $color2["red"] + $err * 7 / 16;
ImageSetPixel($grey_img, $x+1, $y, ImageColorClosest($grey_img,$newgrey, $newgrey, $newgrey));
}
if ($x != 0) {
$color2 = ImageColorsForIndex($grey_img, ImageColorAt($grey_img, $x-1, $y));
$newgrey = $color2["red"] + $err * 3 / 16;
ImageSetPixel($grey_img, $x-1, $y, ImageColorClosest($grey_img,$newgrey, $newgrey, $newgrey));
}
if ($y != ImageSy($src_img)) {
$color2 = ImageColorsForIndex($grey_img, ImageColorAt($grey_img, $x, $y+1));
$newgrey = $color2["red"] + $err * 5 / 16;
ImageSetPixel($grey_img, $x, $y+1, ImageColorClosest($grey_img,$newgrey, $newgrey, $newgrey));
}
if ($x != ImageSx($src_img) && $y != ImageSy($src_img)) {
$color2 = ImageColorsForIndex($grey_img, ImageColorAt($grey_img, $x+1, $y+1));
$newgrey = $color2["red"] + $err / 16;
ImageSetPixel($grey_img, $x+1, $y+1, ImageColorClosest($grey_img,$newgrey, $newgrey, $newgrey));
}
}
}
imagedestroy($grey_img);
}
To output your WBMP, use
ImageWBMP($final_img, "", ImageColorClosest(255,255,255));