note 56249 added to function.imagesetpixel

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. <?php class watermark{ function create_watermark( $dst_img, $watermark_img, $alpha = 100 ) { $alpha /= 100; # convert 0-100% user-friendly alpha to decimal # calculate our images dimensions $dst_img_w = imagesx( $dst_img ); $dst_img_h = imagesy( $dst_img ); $watermark_img_w = imagesx( $watermark_img ); $watermark_img_h = imagesy( $watermark_img ); # create new image to hold merged changes $return_img = imagecreatetruecolor( $dst_img_w, $dst_img_h ); # $return_img = imagecreate( $dst_img_w, $dst_img_h ); # determine center position coordinates $dst_img_min_x = floor( ( $dst_img_w / 2 ) - ( $watermark_img_w / 2 ) ); $dst_img_max_x = ceil( ( $dst_img_w / 2 ) + ( $watermark_img_w / 2 ) ); $dst_img_min_y = floor( ( $dst_img_h / 2 ) - ( $watermark_img_h / 2 ) ); $dst_img_max_y = ceil( ( $dst_img_h / 2 ) + ( $watermark_img_h / 2 ) ); # walk through main image for( $y = 0; $y < $dst_img_h; $y++ ) { for( $x = 0; $x < $dst_img_w; $x++ ) { $return_color = NULL; # determine the correct pixel location within our watermark $watermark_x = $x - $dst_img_min_x; $watermark_y = $y - $dst_img_min_y; # fetch color information for both of our images $dst_rgb = imagecolorsforindex( $dst_img, imagecolorat( $dst_img, $x, $y ) ); # if our watermark has a non-transparent value at this pixel intersection # and we're still within the bounds of the watermark image if ( $watermark_x >= 0 && $watermark_x < $watermark_img_w && $watermark_y >= 0 && $watermark_y < $watermark_img_h ) { $watermark_rbg = imagecolorsforindex( $watermark_img, imagecolorat( $watermark_img, $watermark_x, $watermark_y ) ); # using image alpha, and user specified alpha, calculate average $watermark_alpha = round( ( ( 127 - $watermark_rbg['alpha'] ) / 127 ), 2 ); $watermark_alpha = $watermark_alpha * $alpha; # calculate the color 'average' between the two - taking into account the specified alpha level $avg_red = $this->get_ave_color( $dst_rgb['red'], $watermark_rbg['red'], $watermark_alpha ); $avg_green = $this->get_ave_color( $dst_rgb['green'], $watermark_rbg['green'], $watermark_alpha ); $avg_blue = $this->get_ave_color( $dst_rgb['blue'], $watermark_rbg['blue'], $watermark_alpha ); # calculate a color index value using the average RGB values we've determined $return_color = $this->imagegetcolor( $return_img, $avg_red, $avg_green, $avg_blue ); # if we're not dealing with an average color here, then let's just copy over the main color } else { $return_color = imagecolorat( $dst_img, $x, $y ); } # END if watermark # draw the appropriate color onto the return image imagesetpixel( $return_img, $x, $y, $return_color ); } # END for each X pixel } # END for each Y pixel # return the resulting, watermarked image for display return $return_img; } # END create_watermark() # average two colors given an alpha function get_ave_color( $color_a, $color_b, $alpha ) { return round( ( ( $color_a * ( 1 - $alpha ) ) + ( $color_b * $alpha ) ) ); } # END get_ave_color() # return closest pallette-color match for RGB values function imagegetcolor($im, $r, $g, $b) { $c=imagecolorexact($im, $r, $g, $b); if ($c!=-1) return $c; $c=imagecolorallocate($im, $r, $g, $b); if ($c!=-1) return $c; return imagecolorclosest($im, $r, $g, $b); } # EBD imagegetcolor() } # END watermark API ?> ---- Manual Page -- http://www.php.net/manual/en/function.imagesetpixel.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+56249 Delete: added to the manual -- http://master.php.net/manage/user-notes.php?action=delete+56249&report=yes&reason=added+to+the+manual Delete: bad code -- http://master.php.net/manage/user-notes.php?action=delete+56249&report=yes&reason=bad+code Delete: spam -- http://master.php.net/manage/user-notes.php?action=delete+56249&report=yes&reason=spam Delete: useless -- http://master.php.net/manage/user-notes.php?action=delete+56249&report=yes&reason=useless Delete: non-english -- http://master.php.net/manage/user-notes.php?action=delete+56249&report=yes&reason=non-english Delete: other reasons -- http://master.php.net/manage/user-notes.php?action=delete+56249&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+56249&report=yes Search -- http://master.php.net/manage/user-notes.php