根据icon自适应背景颜色

介绍

本示例将介绍如何根据图片设置自适应的背景色。

效果图预览

使用说明

1. 转换图片为PixelMap，取出所有像素值
2. 遍历所有像素值，查找到出现次数最多的像素，即为图片的主要颜色
3. 适当修改图片的主要颜色，作为自适应的背景色

实现思路

实现步骤

1. 解码图片，转换为PixelMap对象，便于提取像素值
2. 提取所有像素值，转换为整数，放入数组中
3. 遍历数组，将所有像素值放入一个Map中，key为像素值，value为个数
4. 遍历Map，找出出现次数最多的像素值
5. 将整数格式的像素值转换为RGB格式，再转换为HSV格式，参考hue(色调)修改saturation(饱和度)和value(明度)
6. 将HSV格式转换为RGB格式，就得到了背景色

具体实现

1. 将图片转换为PixelMap

   ...
   let pixelMap: image.PixelMap = await image2PixelMap(item.icon);
   ...
   export async function image2PixelMap(icon: string): Promise<image.PixelMap> {
     let rawFileDescriptor: resourceManager.RawFileDescriptor = resourceMgs.getRawFdSync(icon);
     let imageSource: image.ImageSource = image.createImageSource(rawFileDescriptor);
     let pixelMap: image.PixelMap = await imageSource.createPixelMap({
       editable: false,
       desiredPixelFormat: image.PixelMapFormat.BGRA_8888,
       desiredSize: { width: 40, height: 40 }
     })
     return pixelMap;
   }

2. 遍历PixelMap中的所有像素，放到一个数组中

   ...
   let allPixels: number[] = await traverseAllPixel(pixelMap);
   ...
   export async function traverseAllPixel(pixelMap: image.PixelMap): Promise<number[]> {
     const pixelArrayBuffer: ArrayBuffer = new ArrayBuffer(40 * 40 * 4);
     await pixelMap.readPixelsToBuffer(pixelArrayBuffer);
     const allPixels: number[] = [];
     const unit8Pixels: Uint8Array = new Uint8Array(pixelArrayBuffer);
     for (let i = 0; i < unit8Pixels.length; i += 4) {
       const rgb: ColorRgb = {
         red: unit8Pixels[i+2],
         green: unit8Pixels[i+1],
         blue: unit8Pixels[i],
         alpha:unit8Pixels[i+3]
     }
     if (rgb.red === 0 && rgb.green === 0 && rgb.blue === 0 && rgb.alpha === 0) {
       continue;
     }
     allPixels.push(ColorUtils.rgbToNumber(rgb));
     }
     return allPixels;
   }

3. 遍历数组，找到出现次数最多的像素

   ...
   let maxPixel: number = findMaxPixel(allPixels);
   ...
   export function findMaxPixel(allPixels: number[]): number {
     let map: Map<number, number> = new Map();
     allPixels.forEach((pixel: number) => {
       if (map.has(pixel)) {
         map.set(pixel, map.get(pixel)! + 1);
       } else {
         map.set(pixel, 1);
       }
     })
     let maxPixel: number = 0;
     let maxTimes: number = 0;
     map.forEach((value: number, key: number) => {
       if (value >= maxTimes) {
         maxTimes = value;
         maxPixel = key;
       }
     })
     return maxPixel;
   }

4. 将出现次数最多的像素值转换为RGB颜色格式

   ...
   let rgb: ColorRgb = ColorUtils.numberToRgb(maxPixel);
   ...
   public static numberToRgb(color: number): ColorRgb {
     return {
       red: (color & 0xFF0000) >> 16,
       green: (color & 0xFF00) >> 8,
       blue: (color & 0xFF),
       alpha:(color & 0xFF000000)>>24
     }
   }

5. 将RGB颜色格式转换为HSV格式，转换公式如图所示。

   ...
   let hsv: ColorHsv = ColorUtils.rgb2hsv(rgb);
   ...
   public static rgb2hsv(color: ColorRgb): ColorHsv {
     const red: number = color.red / MAX_RGB_VALUE;
     const green: number = color.green / MAX_RGB_VALUE;
     const blue: number = color.blue / MAX_RGB_VALUE;
   
     const max: number = Math.max(red, green, blue);
     const min: number = Math.min(red, green, blue);
     const delta: number = max - min;
   
     let hue: number = 0;
     let saturation: number = 0;
     let value: number = 0;
     if (max === min) {
       hue = 0;
     } else if (max === red) {
       hue = (green >= blue ? ((green - blue) / delta) * 60 : ((green - blue) / delta) * 60 + 360);
     } else if (max === green) {
       hue = (((blue - red) / delta) + 2) * 60;
     } else if (max === blue) {
       hue = (((red - green) / delta) + 4) * 60;
     }
     saturation = (max === 0 ? 0 : delta / max);
     value = max;
   
     return {
       hue: hue,
       saturation: saturation,
       value: value,
       alpha:color.alpha
     }
   }

6. 修改HSV格式中的S和V值，使背景色和图标颜色有明显区分

   ...
   modifySVValue(hsv);
   ...
   export function modifySVValue(color: ColorHsv): void {
     if (color.hue > 20 && color.hue <= 60) {
       color.saturation = 0.12;
       color.value = 0.93;
     } else if (color.hue > 60 && color.hue <= 190) {
       color.saturation = 0.08;
       color.value = 0.91;
     } else if (color.hue > 190 && color.hue <= 270) {
       color.saturation = 0.1;
       color.value = 0.93;
     } else {
       color.saturation = 0.08;
       color.value = 0.93;
     }
   }

7. 将HSV格式转换为RGB格式，转换公式如图所示。

   ...
   rgb = ColorUtils.hsv2rgb(hsv);
   ...
   public static hsv2rgb(color: ColorHsv): ColorRgb {
     const h60: number = color.hue / 60;
     const h60f: number = Math.floor(h60);
     const hi: number = h60f % 6;
     const f: number = h60 - h60f;
     const p: number = color.value * (1 - color.saturation);
     const q: number = color.value * (1 - f * color.saturation);
     const t: number = color.value * (1 - (1 - f) * color.saturation);
   
     let red: number = 0.0;
     let green: number = 0.0;
     let blue: number = 0.0;
     if (hi === 0) {
       red = color.value;
       green = t;
       blue = p;
     } else if (hi === 1) {
       red = q;
       green = color.value;
       blue = p;
     } else if (hi === 2) {
       red = p;
       green = color.value;
       blue = t;
     } else if (hi === 3) {
       red = p;
       green = q;
       blue = color.value;
     } else if (hi === 4) {
       red = t;
       green = p;
       blue = color.value;
     } else if (hi === 5) {
       red = color.value;
       green = p;
       blue = q;
     }
     return {
       red: Math.floor(red * MAX_RGB_VALUE),
       green: Math.floor(green * MAX_RGB_VALUE),
       blue: Math.floor(blue * MAX_RGB_VALUE),
       alpha:color.alpha
     }
   }

8. 将rgb转换为数字，放入AppInfo对象中

   ...
   item.backgroundColor = ColorUtils.rgbToNumber(rgb);
   ...
   public static rgbToNumber(color: ColorRgb): number {
     return ((0xFF << 24) | (color.red << 16) | (color.green << 8) | color.blue);
   }

9. 通过组件的backgroundColor属性设置背景色

   Row() {
   ...
   }
   .backgroundColor(this.item.backgroundColor === '' ? Color.White : this.item.backgroundColor)

高性能知识点

1. 解码图片时，分辨率设为40*40，既可以加快计算背景颜色的速度，又可以保证准确性
2. 提取像素时，由于鸿蒙中的颜色是用{red,green,blue,alpha}来表示，直接放入数组或者Map中会影响计算出现次数最多的像素的速度，所以需要使用rgbToNumber方法转换为整数

工程结构&模块类型

iconmaincolor                                   // har类型
|---mainpage
|   |---MainPage.ets                            // 视图层，主要页面
|---utils
|   |---ColorUtils.ets                          // 颜色处理工具类
|   |---ImageUtils.ets                          // 图片处理工具类

模块依赖

routermodule

参考资料

Image组件