Crazy SVG conversion...

src/Fits.php

@@ -86,8 +86,9 @@ class Fits
     {
         $naxis1 = (int)trim($this->fitsHeader->getKeywordValue('NAXIS1'));
         $naxis2 = (int)trim($this->fitsHeader->getKeywordValue('NAXIS2'));
+        $naxis3 = (int)trim($this->fitsHeader->getKeywordValue('NAXIS3'));
 
-        $blobEnd = $naxis1 * $naxis2;
+        $blobEnd = $naxis1 * $naxis2 * $naxis3;
 
         return substr(
             $this->contents,

src/ImageBlob.php

@@ -13,6 +13,9 @@ class ImageBlob
     private FitsHeader $header;
     public readonly Bitpix $bitpix;
     public readonly int $dataBits;
+    public readonly int $width;
+    public readonly int $height;
+    public readonly int $naxis3;
 
     /**
     * @throws InvalidBitpixValue
@@ -24,18 +27,42 @@ class ImageBlob
         $this->blob = $blob;
         $bitpix = (int) $this->header->keyword('BITPIX')->value;
         $this->bitpix = Bitpix::tryFrom($bitpix) ?? throw new InvalidBitpixValue($bitpix);
-        $naxis1 = (int) trim($this->header->keyword('NAXIS1')->value);
+        $this->width = (int) trim($this->header->keyword('NAXIS1')->value);
-        $naxis2 = (int) trim($this->header->keyword('NAXIS2')->value);
+        $this->height = (int) trim($this->header->keyword('NAXIS2')->value);
-        $this->dataBits = abs($this->bitpix->value) * $naxis1 * $naxis2;
+        $this->naxis3 = (int) trim($this->header->keyword('NAXIS3')->value);
+        $this->dataBits = abs($this->bitpix->value) * $this->width * $this->height * $this->naxis3;
     }
     /**
     * Returns a generator that yields image data
-    * byte by byte
+    * pixel by pixel
     */
-    public function dataBytes(): \Generator
+    public function pixels(): \Generator
     {
+        $n = 0;
+        $pixel = [];
+        $pixBytes = abs($this->bitpix->value) / 8;
+
         for ($i = 0; $i < strlen($this->blob); $i++) {
-            yield $this->blob[$i];
+            $value = unpack(
+                format: 'C',
+                string: $this->blob[$i]
+            )[1];
+
+            //$value = floor($value / 256);
+
+            if ($i + $pixBytes <= strlen($this->blob) - 1) {
+                $value += unpack(
+                    format: 'C',
+                    string: $this->blob[$i + $pixBytes - 1]
+                )[1];
+            }
+
+            $pixel[$n] = $value;
+            $n++;
+            if ($n === $this->naxis3) {
+                $n = 0;
+                yield $pixel;
+            }
         }
     }
     /**
@@ -48,4 +75,42 @@ class ImageBlob
         $gdImg = imagecreatefromstring($this->blob);
         return imagepng($gdImg, quality: $quality);
     }
+
+    /**
+    * Convert to SVG for display
+    * @todo This assumes RGB and produces a gigantic file...
+    * Note: pixels are treated as SVG rectangles, RGB values are
+            extracted from bit values... (?!)
+    */
+    public function toSVG(): string
+    {
+        $svg = <<<SVG
+            <svg version="1.1"
+                width="{$this->width}"
+                height="{$this->height}"
+            xmlns="http://www.w3.org/2000/svg">
+
+        SVG;
+        $x = 1;
+        $y = 1;
+        $cols = 1;
+        // Build SVG using 1x1 rectangles
+        foreach ($this->pixels() as $k => $pixel) {
+            // A pixel is a 3-element array if the image is RGB
+            [$r, $g, $b] = $pixel;
+            $r = $r / 2;
+            $g = $g / 2;
+            $b = $b / 2;
+            // Change row after reaching image width
+            if ($x === $this->width + 1) {
+                $y++;
+                $x = 1;
+            }
+            $svg .= "<rect x=\"$x\" y=\"$y\" width=\"1\" height=\"1\" fill=\"rgb($r, $g, $b)\" />\n";
+            $x++;
+        }
+        $svg .= '</svg>';
+
+        return $svg;
+    }
 }

tests/ImageBlobTest.php

@@ -26,7 +26,7 @@ final class ImageBlobTest extends TestCase
 
     public function testDataBitsLength(): void
     {
-        $this->assertSame($this->imageBlob->dataBits, 16*2448*1669);
+        $this->assertSame($this->imageBlob->dataBits, 16*2448*1669*3);
     }
 }