improve image coloring

dist/types/plugins/utils/image-contrast.d.ts

@@ -1 +1,2 @@
 export declare function contrastImage(imgData: ImageData, refContrast: number): ImageData;
+export declare function normalizeContrast(image: ImageData): ImageData;

dist/types/plugins/utils/image-grayscale.d.ts

@@ -0,0 +1,2 @@
+export declare function vFromRGB(r: number, g: number, b: number): number;
+export declare function grayscale(image: ImageData): ImageData;

src/plugins/utils/image-contrast.ts

@@ -1,3 +1,5 @@
+import { vFromRGB } from "./image-grayscale";
+
 export function contrastImage(imgData: ImageData, refContrast: number) {
   //input range [-100..100]
   const d = imgData.data;
@@ -11,3 +13,26 @@ export function contrastImage(imgData: ImageData, refContrast: number) {
   }
   return imgData;
 }
+
+
+export function normalizeContrast(image: ImageData) {
+    const data = image.data;
+    let max = 0;
+    let min = 255;
+
+    // Find the max and min luminance values
+    for (let i = 0; i < data.length; i += 4) {
+        let luminance = vFromRGB(data[i], data[i + 1], data[i + 2]);
+        max = Math.max(max, luminance);
+        min = Math.min(min, luminance);
+    }
+
+    // Normalize the contrast
+    for (let i = 0; i < data.length; i += 4) {
+        data[i] = 255 * (data[i] - min) / (max - min);     // Red
+        data[i + 1] = 255 * (data[i + 1] - min) / (max - min); // Green
+        data[i + 2] = 255 * (data[i + 2] - min) / (max - min); // Blue
+    }
+
+    return image;
+}

src/plugins/utils/image-grayscale.ts

@@ -0,0 +1,16 @@
+export function vFromRGB(r: number, g: number, b: number) {
+  return 0.299 * r + 0.587 * g + 0.114 * b;
+}
+
+export function grayscale(image: ImageData) {
+  let d = image.data;
+  for (let i = 0; i < d.length; i += 4) {
+    let r = d[i];
+    let g = d[i + 1];
+    let b = d[i + 2];
+    let v = vFromRGB(r, g, b)
+    d[i] = d[i + 1] = d[i + 2] = v;
+  }
+
+  return image;
+}

src/plugins/utils/sobel-operator.ts

@@ -1,3 +1,5 @@
+import { vFromRGB } from "./image-grayscale";
+
 let fId = 0;
 export class HistogramFrame extends Array<number> {
   id: number;
@@ -16,9 +18,11 @@ export function sobelOperator(imgData: ImageData) {
   // convert to grayscale
   let ii = 0;
   for (let i = 0; i < imgData.data.length; i += 4) {
-    let gray =
-      (imgData.data[i] + imgData.data[i + 1] + imgData.data[i + 2]) / 3;
-    grayscale[ii] = gray;
+    grayscale[ii] = vFromRGB(
+      imgData.data[i],
+      imgData.data[i + 1],
+      imgData.data[i + 2]
+    );
     ii++;
   }