/**
* Generates a portion of an ImageMagick convert command to apply an alpha mask
*
* Note: More accurate values for radii used to generate the LASCO C2 & C3 alpha masks:
* rocc_outer = 7.7; // (.9625 * orig)
* rocc_inner = 2.415; // (1.05 * orig)
*
* LASCO C2 Image Scale
* $lascoC2Scale = 11.9;
*
* Solar radius in arcseconds, source: Djafer, Thuillier and Sofia (2008)
* $rsunArcSeconds = 959.705;
* $rsun = $rsunArcSeconds / $lascoC2Scale;
* = 80.647 // Previously, used hard-coded value of 80.814221
*
* Generating the alpha masks:
* $rocc_inner = 2.415;
* $rocc_outer = 7.7;
*
* // convert to pixels
* $radius_inner = $rocc_inner * $rsun;
* $radius_outer = $rocc_outer * $rsun;
* $innerCircleY = $crpix2 + $radius_inner;
* $outerCircleY = $crpix2 + $radius_outer;
*
* exec("convert -size 1024x1024 xc:black -fill white -draw \"circle $crpix1,$crpix2 $crpix1,$outerCircleY\"
* -fill black -draw \"circle $crpix1,$crpix2 $crpix1,$innerCircleY\" +antialias LASCO_C2_Mask.png")
*
* Masks have been pregenerated and stored in order to improve performance.
*
* Note on offsets:
*
* The original CRPIX1 and CRPIX2 values used to determine the location of the center of the sun in the image
* are specified with respect to a bottom-left corner origin. The values passed in to this method from the tile
* request, however, specify the offset with respect to a top-left corner origin. This simply makes things
* a bit easier since ImageMagick also treats images as having a top-left corner origin.
*
* Region of interest:
*
* The region of interest (ROI) below is specified at the original JP2 image scale.
*
* @param object $imagickImage an initialized Imagick object
*
* @return void
*/
protected function setAlphaChannel(&$imagickImage)
{
$maskWidth = 1040;
$maskHeight = 1040;
$mask = HV_ROOT_DIR . '/resources/images/alpha-masks/LASCO_' . $this->uiLabels[2]['name'] . '_Mask.png';
if ($this->reduce > 0) {
$maskScaleFactor = 1 / pow(2, $this->reduce);
} else {
$maskScaleFactor = 1;
}
$maskTopLeftX = ($this->imageSubRegion['left'] + ($maskWidth - $this->jp2->getWidth()) / 2 - $this->offsetX) * $maskScaleFactor;
$maskTopLeftY = ($this->imageSubRegion['top'] + ($maskHeight - $this->jp2->getHeight()) / 2 - $this->offsetY) * $maskScaleFactor;
$width = $this->subfieldWidth * $maskScaleFactor;
$height = $this->subfieldHeight * $maskScaleFactor;
// $maskTopLeft coordinates cannot be negative when cropping, so if they are, adjust the width and height
// by the negative offset and crop with zero offsets. Then put the image on the properly-sized image
// and offset it correctly.
$cropWidth = round($width + min($maskTopLeftX, 0));
$cropHeight = round($height + min($maskTopLeftY, 0));
$mask = new IMagick($mask);
// Imagick floors pixel values but they need to be rounded up or down.
// Rounding cannot be done in the previous lines of code because some addition needs to take place first.
$maskTopLeftX = round($maskTopLeftX);
$maskTopLeftY = round($maskTopLeftY);
$width = round($width);
$height = round($height);
$mask->scaleImage($maskWidth * $maskScaleFactor, $maskHeight * $maskScaleFactor);
$mask->cropImage($cropWidth, $cropHeight, max($maskTopLeftX, 0), max($maskTopLeftY, 0));
$mask->resetImagePage($width . 'x' . $height . '+0+0');
$mask->setImageBackgroundColor('black');
$mask->extentImage($width, $height, $width - $cropWidth, $height - $cropHeight);
$imagickImage->setImageExtent($width, $height);
$imagickImage->compositeImage($mask, IMagick::COMPOSITE_COPYOPACITY, 0, 0);
if ($this->options['opacity'] < 100) {
$mask->negateImage(true);
$imagickImage->setImageClipMask($mask);
$imagickImage->setImageOpacity($this->options['opacity'] / 100);
}
$mask->destroy();
}
