Fix dithered gradients having wrong colors

Pass a nx1 image instead of the GradientTexture, that contains all of the gradient's selected colors, where n is the number of colors.

src/Shaders/Gradients/Linear.gdshader

@@ -14,7 +14,7 @@ uniform int repeat = 0; // 0 = none, 1 = repeat, 2 = mirrored, 3 = truncate
 
 float modify_uv(vec2 uv) {
 	float modified_uv;
-	if (shape == 0) {
+	if (shape == 0) { // Linear
 		vec2 uv_offsetted = uv - 0.5;
 		float angle_cos = cos(radians(angle));
 		float angle_sin = sin(radians(angle));
@@ -24,7 +24,7 @@ float modify_uv(vec2 uv) {
 		float pivot = position / size;
 		modified_uv -= pivot - 0.5;
 	}
-	else {
+	else { // Radial
 		vec2 uv_offsetted = uv * 2.0 - 1.0;
 		uv_offsetted -= (center * 2.0) - vec2(1.0);
 		uv_offsetted *= radius;
@@ -33,6 +33,7 @@ float modify_uv(vec2 uv) {
 	return modified_uv;
 }
 
+
 float mirror_fract(float uv) {
 	int sign_uv = (int(sign(uv)) - 1) / 2;
 	if (int((uv)) % 2 == sign_uv)

src/Shaders/Gradients/LinearDithering.gdshader

@@ -19,7 +19,7 @@ uniform int n_of_colors = 2;
 
 float modify_uv(vec2 uv) {
 	float modified_uv;
-	if (shape == 0) {
+	if (shape == 0) { // Linear
 		vec2 uv_offsetted = uv - 0.5;
 		float angle_cos = cos(radians(angle));
 		float angle_sin = sin(radians(angle));
@@ -29,7 +29,7 @@ float modify_uv(vec2 uv) {
 		float pivot = position / size;
 		modified_uv -= pivot - 0.5;
 	}
-	else {
+	else { // Radial
 		vec2 uv_offsetted = uv * 2.0 - 1.0;
 		uv_offsetted -= (center * 2.0) - vec2(1.0);
 		uv_offsetted *= radius;
@@ -52,7 +52,7 @@ float mirror_fract(float uv) {
 // Logic taken from https://godotshaders.com/shader/dither-gradient-shader/
 float dither(vec2 uv, float modified_uv) {
 	float uv_lower = floor(modified_uv);
-	float uv_upper = (floor(modified_uv) + 1.0);
+	float uv_upper = floor(modified_uv) + 1.0;
 	float threshold = texture(dither_texture, uv * (image_size / float(pixel_size))).r;
 	float ramp_val = modified_uv < threshold ? 0.0 : 1.0;
 	// sample at the lower bound colour if ramp_val is 0.0, upper bound color if 1.0

src/UI/Dialogs/ImageEffects/GradientDialog.gd

@@ -70,22 +70,34 @@ func commit_action(cel: Image, project: Project = Global.current_project) -> voi
 
 	var dither_texture: Texture = selected_dither_matrix.texture
 	var pixel_size := dither_texture.get_width()
-	var gradient: Gradient = gradient_edit.texture.gradient
+	var gradient: Gradient = gradient_edit.gradient
 	var n_of_colors := gradient.offsets.size()
 	# Pass the gradient offsets as an array to the shader
 	# ...but since Godot 3.x doesn't support uniform arrays, instead we construct
 	# a nx1 grayscale texture with each offset stored in each pixel, and pass it to the shader
 	var offsets_image := Image.new()
 	offsets_image.create(n_of_colors, 1, false, Image.FORMAT_L8)
+	# Construct an image that contains the selected colors of the gradient without interpolation
+	var gradient_image := Image.new()
+	gradient_image.create(n_of_colors, 1, false, Image.FORMAT_RGBA8)
 	offsets_image.lock()
+	gradient_image.lock()
 	for i in n_of_colors:
 		var c := gradient.offsets[i]
 		offsets_image.set_pixel(i, 0, Color(c, c, c, c))
+		gradient_image.set_pixel(i, 0, gradient.colors[i])
 	offsets_image.unlock()
+	gradient_image.unlock()
 	var offsets_tex := ImageTexture.new()
 	offsets_tex.create_from_image(offsets_image, 0)
+	var gradient_tex: Texture
+	if shader == shader_linear:
+		gradient_tex = gradient_edit.texture
+	else:
+		gradient_tex = ImageTexture.new()
+		gradient_tex.create_from_image(gradient_image, 0)
 	var params := {
-		"gradient_texture": gradient_edit.texture,
+		"gradient_texture": gradient_tex,
 		"offset_texture": offsets_tex,
 		"selection": selection_tex,
 		"repeat": repeat_option_button.selected,