Add edgeNpixels shader (#630)

Co-authored-by: Andrei Timofeev <andrei.timofeev@mobirate.com>

pixel-art-scaling/edgeNpixels.slangp

@@ -0,0 +1,5 @@
+shaders = 1
+
+shader0 = shaders/edgeNpixels.slang
+filter_linear0 = true
+scale_type0 = viewport

pixel-art-scaling/shaders/edge1pixel.slang

@@ -1,6 +1,7 @@
 #version 450
 
-// Interpolate a single row of display pixels between each pair of adjacent source pixels.
+// Insert a single interpolated display (high-res)
+// pixel row between each pair of adjacent source (low-res) pixels.
 // by decavoid
 
 
@@ -20,22 +21,21 @@ layout(std140, set = 0, binding = 0) uniform UBO
 #pragma stage vertex
 layout(location = 0) in vec4 Position;
 layout(location = 1) in vec2 TexCoord;
-layout(location = 0) out vec2 vTexCoord;
-layout(location = 1) out vec2 inverseScale;
+layout(location = 0) out vec2 PixelCoords;
 
 void main()
 {
    gl_Position = global.MVP * Position;
-   vTexCoord = TexCoord;
-   inverseScale = vec2(params.OriginalSize.xy / params.OutputSize.xy);
+   PixelCoords = TexCoord * params.SourceSize.xy; // NES x: [0; 256], y: [0; 240]
 }
 
 #pragma stage fragment
-layout(location = 0) in vec2 vTexCoord;
-layout(location = 1) in vec2 inverseScale;
+layout(location = 0) in vec2 PixelCoords;
 layout(location = 0) out vec4 FragColor;
 layout(set = 0, binding = 2) uniform sampler2D Source;
 
+vec2 inverseScaleHalf = vec2(params.OriginalSize.xy / params.OutputSize.xy) * 0.5;
+
 vec2 isInside(vec2 v, vec2 left, vec2 right)
 {
 	return step(left, v) - step(right, v);
@@ -46,11 +46,11 @@ vec2 isInside(vec2 v, vec2 left, vec2 right)
 
 void main()
 {
-	vec2 pixelCoords = vTexCoord * params.SourceSize.xy; // NES x: [0; 256], y: [0; 240]
-	vec2 coordAtPixelCenter = (floor(pixelCoords) + vec2(0.5));
-	vec2 coordBetweenPixels = round(pixelCoords);
-	vec2 f = fract(pixelCoords) + vec2(1e-4);
-	vec2 isFractionInside = isInside(f, 0.5 * inverseScale, 1.0 - 0.5 * inverseScale);
+	vec2 iPixelCoords = floor(PixelCoords);
+	vec2 coordAtPixelCenter = iPixelCoords + vec2(0.5);
+	vec2 coordBetweenPixels = round(PixelCoords);
+	vec2 f = fract(PixelCoords) + vec2(1e-3);
+	vec2 isFractionInside = isInside(f, inverseScaleHalf, 1.0 - inverseScaleHalf);
 
 /*
 	Equivalent:
@@ -67,7 +67,7 @@ void main()
 */
 
 	vec2 newCoord = isFractionInside * coordAtPixelCenter + (1 - isFractionInside) * coordBetweenPixels;
-	vec2 newTexCoord = newCoord / params.SourceSize.xy;
+	vec2 newTexCoord = newCoord * params.SourceSize.zw;
 	FragColor = texture(Source, newTexCoord);
 
 #ifdef DEBUG_DRAW_EDGES

pixel-art-scaling/shaders/edgeNpixels.slang

@@ -0,0 +1,74 @@
+#version 450
+
+// Insert a configurable count (1, 2, 3...) of interpolated display (high-res)
+// pixel rows between each pair of adjacent source (low-res) pixels.
+// by decavoid
+
+
+#pragma parameter PixelCount "Pixel Count" 2.0 1.0 8.0 1.0
+
+layout(push_constant) uniform Push
+{
+	vec4 SourceSize;
+	vec4 OriginalSize;
+	vec4 OutputSize;
+	uint FrameCount;
+	float PixelCount;
+} params;
+
+layout(std140, set = 0, binding = 0) uniform UBO
+{
+	mat4 MVP;
+} global;
+
+
+#pragma stage vertex
+layout(location = 0) in vec4 Position;
+layout(location = 1) in vec2 TexCoord;
+layout(location = 0) out vec2 PixelCoords;
+
+void main()
+{
+   gl_Position = global.MVP * Position;
+	PixelCoords = TexCoord * params.SourceSize.xy; // NES x: [0; 256], y: [0; 240]
+}
+
+#pragma stage fragment
+layout(location = 0) in vec2 PixelCoords;
+layout(location = 0) out vec4 FragColor;
+layout(set = 0, binding = 2) uniform sampler2D Source;
+
+// uncomment to see a red grid of modified pixels
+//#define DEBUG_DRAW_EDGES
+
+vec4 sizeScale = params.OutputSize / params.OriginalSize;
+vec2 interpolationRangeHalf = params.PixelCount * 0.5 * sizeScale.zw;
+float stepPerRow = 1.0 / (params.PixelCount + 1.0);
+
+void main()
+{
+	vec2 coordAtPixelCenter = (floor(PixelCoords) + vec2(0.5));
+	vec2 coordBetweenPixels = round(PixelCoords);
+	vec2 origOffset = PixelCoords - coordBetweenPixels + 1e-3; // [-0.5; 0.5]
+
+	vec2 needInterpolate = step(abs(origOffset), interpolationRangeHalf);
+
+	// if needInterpolate == 0, disable interpolation by choosing coordAtPixelCenter.
+	//
+	// if needInterpolate == 1, transform origOffset.x
+	// from range [-interpolationRangeHalf.x; interpolationRangeHalf.x]
+	// to range (-0.5; 0.5)
+	vec2 segmentIndex = floor((origOffset + interpolationRangeHalf) * sizeScale.xy);
+	vec2 transformedOffset = stepPerRow * (segmentIndex + 1) - 0.5;
+	vec2 interpolatedCoord = coordBetweenPixels + transformedOffset;
+
+	vec2 newCoord = (1 - needInterpolate) * coordAtPixelCenter + needInterpolate * interpolatedCoord;
+	vec2 newTexCoord = newCoord * params.SourceSize.zw;
+
+	FragColor = texture(Source, newTexCoord);
+
+#ifdef DEBUG_DRAW_EDGES
+	if (needInterpolate.x + needInterpolate.y > 0)
+		FragColor.r = 1;
+#endif
+}