[api]: Take account of DATAMIN and DATAMAX FITS keywords

tiagohm · Apr 5, 2024 · 8437bec · 8437bec
1 parent 8fb505f
commit 8437bec
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Showing 3 changed files with 22 additions and 2 deletions.
diff --git a/nebulosa-fits/src/main/kotlin/nebulosa/fits/FitsFormat.kt b/nebulosa-fits/src/main/kotlin/nebulosa/fits/FitsFormat.kt
@@ -66,8 +66,11 @@ data object FitsFormat : ImageFormat {
         val numberOfChannels = header.numberOfChannels
         val bitpix = header.bitpix
         val position = source.position
+        val rangeMin = header.getFloat(FitsKeyword.DATAMIN, 0f)
+        val rangeMax = header.getFloat(FitsKeyword.DATAMAX, 1f)
+        val range = rangeMin..rangeMax
 
-        val data = SeekableSourceImageData(source, position, width, height, numberOfChannels, bitpix)
+        val data = SeekableSourceImageData(source, position, width, height, numberOfChannels, bitpix, range)
         val skipBytes = computeRemainingBytesToSkip(data.totalSizeInBytes)
         if (skipBytes > 0L) source.seek(position + data.totalSizeInBytes + skipBytes)
 

diff --git a/nebulosa-fits/src/main/kotlin/nebulosa/fits/SeekableSourceImageData.kt b/nebulosa-fits/src/main/kotlin/nebulosa/fits/SeekableSourceImageData.kt
@@ -3,6 +3,7 @@ package nebulosa.fits
 import nebulosa.fits.FitsFormat.readPixel
 import nebulosa.image.format.ImageChannel
 import nebulosa.image.format.ImageData
+import nebulosa.image.format.ImageData.Companion.representableRange
 import nebulosa.io.SeekableSource
 import okio.Buffer
 import okio.Sink
@@ -16,8 +17,12 @@ internal data class SeekableSourceImageData(
     override val height: Int,
     override val numberOfChannels: Int,
     private val bitpix: Bitpix,
+    private val range: ClosedFloatingPointRange<Float>,
 ) : ImageData {
 
+    private val rangeDelta = range.endInclusive - range.start
+    private val rescale = range.start != 0f || range.endInclusive != 1f
+
     @JvmField internal val channelSizeInBytes = (numberOfPixels * bitpix.byteLength).toLong()
     @JvmField internal val totalSizeInBytes = channelSizeInBytes * numberOfChannels
 
@@ -84,7 +89,9 @@ internal data class SeekableSourceImageData(
                 n = (size / bitpix.byteLength).toInt()
 
                 repeat(n) {
-                    output[pos++] = buffer.readPixel(bitpix)
+                    val pixel = buffer.readPixel(bitpix)
+                    output[pos++] = if (rescale) pixel.representableRange(range.start, range.endInclusive, rangeDelta)
+                    else pixel
                 }
 
                 remainingPixels -= n

diff --git a/nebulosa-image-format/src/main/kotlin/nebulosa/image/format/ImageData.kt b/nebulosa-image-format/src/main/kotlin/nebulosa/image/format/ImageData.kt
@@ -18,4 +18,14 @@ interface ImageData {
     val blue: FloatArray
 
     fun readChannelTo(channel: ImageChannel, output: FloatArray)
+
+    companion object {
+
+        @Suppress("NOTHING_TO_INLINE")
+        inline fun Float.representableRange(rangeMin: Float, rangeMax: Float, rangeDelta: Float = rangeMax - rangeMin): Float {
+            return if (this < rangeMin) 0f
+            else if (this > rangeMax) 1f
+            else (this - rangeMin) / rangeDelta
+        }
+    }
 }