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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。RGB转为HSV

    ...
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。HSV转为RGB

    ...
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