Add basic geometry correction

And a bit of a refactor...

src/fingerprint.cpp

@@ -15,19 +15,19 @@ Satellite fingerprint_ccsds_frames(std::istream &stream) {
     for (size_t i = 0; i < 50; i++) {
         stream.read(reinterpret_cast<char *>(frame), 1024);
         if (frame[0] != 0x1A || frame[1] != 0xCF || frame[2] != 0xFC || frame[3] != 0x1D) {
-            return Satellite_Unknown;
+            return Satellite::Unknown;
         }
         uint8_t VCID = frame[5] & 0x3f; // 0b111111
         virtual_channels[VCID]++;
     }
 
     // Perform virtual channel analysis
     if (virtual_channels[5] > 12) {
-        return Satellite_Fengyun;
+        return Satellite::FengYun;
     } else if (virtual_channels[9] > 8) {
-        return Satellite_MetOp;
+        return Satellite::MetOp;
     } else {
-        return Satellite_Meteor;
+        return Satellite::Meteor;
     }
 }
 
@@ -44,7 +44,7 @@ Satellite fingerprint_ccsds_data(std::istream &stream) {
         stream.read(reinterpret_cast<char *>(buffer), 1024);
         if (deframer.work(buffer, frame, 1024)) {
             if (frame[10] == 0 && frame[11] == 0 && frame[12] == 0 && frame[13] == 0) {
-                return Satellite_Meteor;
+                return Satellite::Meteor;
             }
 
             frames++;
@@ -56,13 +56,13 @@ Satellite fingerprint_ccsds_data(std::istream &stream) {
 
     if (frames > 50) {
         if (virtual_channels[5] > frames/10) {
-            return Satellite_Fengyun;
+            return Satellite::FengYun;
         } else if (virtual_channels[9] > frames/10) {
-            return Satellite_MetOp;
+            return Satellite::MetOp;
         }
     }
 
-    return Satellite_Unknown;
+    return Satellite::Unknown;
 }
 
 bool is_noaa(std::istream &stream) {
@@ -89,29 +89,29 @@ bool is_noaa(std::istream &stream) {
 Satellite fingerprint(std::string filename) {
     std::filebuf file = std::filebuf();
     if (!file.open(filename, std::ios::in | std::ios::binary)) {
-        return Satellite_Unknown;
+        return Satellite::Unknown;
     }
     std::istream stream(&file);
 
     Satellite satellite = fingerprint_ccsds_frames(stream);
-    if (satellite != Satellite_Unknown) {
+    if (satellite != Satellite::Unknown) {
         file.close();
         return satellite;
     }
 
     stream.seekg(stream.beg);
     satellite = fingerprint_ccsds_data(stream);
-    if (satellite != Satellite_Unknown) {
+    if (satellite != Satellite::Unknown) {
         file.close();
         return satellite;
     }
 
     stream.seekg(stream.beg);
     if (is_noaa(stream)) {
         file.close();
-        return Satellite_NOAA;
+        return Satellite::NOAA;
     }
 
     file.close();
-    return Satellite_Unknown;
+    return Satellite::Unknown;
 }

src/fingerprint.h

@@ -1,7 +1,8 @@
 #ifndef LEANHRPT_FINGERPRINT_H
 #define LEANHRPT_FINGERPRINT_H
 
-#include "mainwindow.h"
+#include "satinfo.h"
+#include <string>
 
 Satellite fingerprint(std::string filename);
 

src/geometry.cpp

@@ -0,0 +1,56 @@
+/*
+ * LeanHRPT Decode
+ * Copyright (C) 2021 Xerbo
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "geometry.h"
+
+#include <cmath>
+
+// Convert from a internal angle of a circle to the viewing angle of a point above the circle.
+float earth2sat_angle(float radius, float height, float angle) {
+    return -std::atan(std::sin(angle)*radius / (std::cos(angle)*radius - (radius+height)));
+}
+
+// Based off https://github.com/Xerbo/meteor_corrector
+QImage correct_geometry(QImage image, Satellite satellite) {
+    const SatelliteInfo info = satellite_info.at(satellite);
+    const size_t output_width = info.swath/info.resolution;
+
+    size_t *lut = new size_t[output_width];
+
+    float view_angle = info.swath / EARTH_RADIUS;
+    float sat_edge = earth2sat_angle(EARTH_RADIUS, info.orbit_height, view_angle/2);
+
+    // Compute a look up table of pixel positions
+    for (size_t x = 0; x < output_width; x++) {
+        float angle = (static_cast<float>(x)/static_cast<float>(output_width) - 0.5f) * view_angle;
+        angle = earth2sat_angle(EARTH_RADIUS, info.orbit_height, angle);
+
+        lut[x] = (angle/sat_edge + 1.0f)/2.0f * static_cast<float>(image.width());
+    }
+
+    // Copy pixels over from the source to the corrected image
+    QImage corrected(output_width, image.height(), image.format());
+    for (size_t y = 0; y < static_cast<size_t>(image.height()); y++) {
+        for (size_t x = 0; x < output_width; x++) {
+            corrected.setPixel(x, y, image.pixel(lut[x], y));
+        }
+    }
+
+    delete[] lut;
+    return corrected;
+}

src/geometry.h

@@ -0,0 +1,28 @@
+/*
+ * LeanHRPT Decode
+ * Copyright (C) 2021 Xerbo
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef LEANHRPT_GEOMETRY_H
+#define LEANHRPT_GEOMETRY_H
+
+#include <QImage>
+
+#include "satinfo.h"
+
+QImage correct_geometry(QImage image, Satellite satellite);
+
+#endif