libcamera: software_isp: GPU support for unpacked 10/12-bit formats

The GPU processing supports 8-bit sensor formats and 10/12-bit packed
formats.  Support for 10/12-bit unpacked formats is missing, let's add
it.

10/12-bit unpacked formats use two adjacent bytes to store the value.
This means the 8-bit shaders can be used if we can modify them for
additional support of 16-bit addressing.  This requires the following
modifications:

- Using GL_RG (two bytes per pixel) instead of GL_LUMINANCE (one byte
  per pixel) as the texture format for the given input formats.

- Setting the texture width to the number of pixels rather than the
  number of bytes.

- Making the definition of `fetch' macro variable, according to the
  pixel format.

- Using only `fetch' for accessing the texture.

Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>

include/libcamera/internal/shaders/bayer_8.frag

@@ -32,9 +32,17 @@ uniform mat3		ccm;
 void main(void) {
     vec3 rgb;
 
+    #if defined(RAW10P)
+    #define pixel(p) p.r / 4.0 + p.g * 64.0
+    #define fetch(x, y) pixel(texture2D(tex_y, vec2(x, y)))
+    #elif defined(RAW12P)
+    #define pixel(p) p.r / 16.0 + p.g * 16.0
+    #define fetch(x, y) pixel(texture2D(tex_y, vec2(x, y)))
+    #else
     #define fetch(x, y) texture2D(tex_y, vec2(x, y)).r
+    #endif
 
-    float C = texture2D(tex_y, center.xy).r; // ( 0, 0)
+    float C = fetch(center.x, center.y); // ( 0, 0)
     const vec4 kC = vec4( 4.0,  6.0,  5.0,  5.0) / 8.0;
 
     // Determine which of four types of pixels we are on.