v2.0, better quality, less perspective deformation (#1)

Reviewed-on: #1

README.md

@@ -4,7 +4,7 @@ Shaders for Avidemux with OpenGL support
 
 ## GoPro fisheye removal v2.0
 
-![Sample image](https://blog.rozk.net/wp-content/uploads/2025/07/compare.png)
+![Sample image](https://blog.rozk.net/wp-content/uploads/2025/10/preview_fisheye_removal.jpg)
 
 ### gopro_8:7 - Fisheye removal for GoPro 11+, 8:7 ratio, 4K, HyperSmooth off
 
@@ -13,12 +13,12 @@ Shaders for Avidemux with OpenGL support
 - New method based on sensor size and focal length
 - Accurate frame widening
 - Fisheye aware subsampling
-- Rec.709 colorspace conversion _(requires to patch and rebuild Avidemux)_
+- Rec.709 colorspace conversion
 
 #### Content
 
 - avidemux.patch  
-A patch to use GL_NEAREST instead of GL_LINEAR for the luminance channel (the shader is implementing bilinear interpolation with colorspace conversion).
+Optional patch to use GL_NEAREST instead of GL_LINEAR for the luminance channel (the shader is implementing bilinear interpolation with colorspace conversion).
 
 - unfish_gopro_8:7.py  
 Script to compute the parameters
@@ -44,3 +44,9 @@ _For commercial OS's, figure out the paths yourself, then edit the preset to fix
 - Select "Custom/preset_gopro_8:7" in the menu
 - Modify and/or add filters
 - Save the video
+
+#### Shader options
+
+- #define color_conversion: comment out to disable gamma correction for the luminance channel
+- #define texture_filtering: comment out to disable custom bilinear filtering for the luminance channel
+- #define rotate_180: uncomment to rotate the image by 180 degrees

gopro_8:7/preset_gopro_8:7.py

@@ -103,7 +103,7 @@ adm.addVideoFilter(
     "shaderLoader", "shaderFile=/opt/rk/avidemux/unfish_gopro_8:7.glsl")
 adm.addVideoFilter(
     "swscale",
-    "width=2832",
+    "width=2468",
     "height=2160",
     "algo=2",
     "sourceAR=0",

gopro_8:7/unfish_gopro_8:7.glsl

@@ -37,7 +37,6 @@ uniform float pts;
 // parameters
 
 const vec2  sensor_size              = vec2(5.949440, 5.205760);
-const vec2  rectilinear_scale        = vec2(1.147370, 1.0);
 const float equidistant_focal_length = 2.920000;
 const float rectilinear_focal_length = 2.102263;
 
@@ -56,7 +55,7 @@ vec2 sensor_to_texture;
 
 void initialize() {
     texture_center = myResolution * 0.5;
-    texture_to_sensor = (sensor_size / myResolution) * rectilinear_scale;
+    texture_to_sensor = (sensor_size / myResolution);
 #ifdef rotate_180
     texture_to_sensor *= -1.0;
 #endif

gopro_8:7/unfish_gopro_8:7.py

@@ -87,26 +87,19 @@ print("linear fov  : horizontal = %7.3f, vertical = %7.3f, diagonal = %7.3f (deg
 
 print("\n--- shader parameters ---\n")
 
-output_size_horizontal = 2.0 * rectilinear_radius(gopro_fov_horizontal * 0.5)
-output_size_vertical   = gopro_size_vertical
-
-output_scale_horizontal = output_size_horizontal / gopro_size_horizontal
-
 print("""// parameters\n
 const vec2  sensor_size              = vec2(%.6f, %.6f);
-const vec2  rectilinear_scale        = vec2(%.6f, 1.0);
 const float equidistant_focal_length = %.6f;
 const float rectilinear_focal_length = %.6f;""" % (
     gopro_size_horizontal, gopro_size_vertical,
-    output_scale_horizontal,
     gopro_focal_length,
     rectilinear_focal_length_vertical)
 )
 
-print("\n--- filters parameters ---\n")
+print("\n--- output size ---\n")
 
 def print_output_array(array_vertical):
-    array_horizontal = (array_vertical / gopro_array_vertical) * gopro_array_horizontal * output_scale_horizontal
+    array_horizontal = (array_vertical / gopro_array_vertical) * gopro_array_horizontal
     print("resize: width = %d, height = %d" % (
         round(array_horizontal / 4.0) * 4,
         array_vertical))