Android中如何获取RGB色轮内指定颜色的X、Y坐标（Java实现）

Got it, here's a straightforward, practical approach to locate your target color in the color wheel PNG and move an indicator to that position using Android/Java code:

Step 1: Convert the Color Wheel Image to a Bitmap #

First, you need a Bitmap instance of your color wheel to access its pixel data. You can get this either from an existing ImageView or directly from your drawable resources:

From an ImageView: #

ImageView colorWheelIv = findViewById(R.id.color_wheel_image);
colorWheelIv.setDrawingCacheEnabled(true);
Bitmap colorWheelBitmap = Bitmap.createBitmap(colorWheelIv.getDrawingCache());
colorWheelIv.setDrawingCacheEnabled(false); // Disable cache once we have the bitmap

From Drawable Resources: #

Bitmap colorWheelBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.rgb_color_wheel);

Step 2: Scan the Bitmap for Your Target Color #

Now iterate through each pixel to find matches with your target color (#6DFFE0 here). Android uses ARGB color values, so we’ll handle alpha transparency (if needed) and either look for an exact match or use a tolerance for anti-aliased images.

Exact Color Match (For Non-Anti-Aliased Wheels): #

int targetColor = Color.parseColor("#6DFFE0");
int width = colorWheelBitmap.getWidth();
int height = colorWheelBitmap.getHeight();

Point targetPoint = null;

for (int y = 0; y < height; y++) {
    for (int x = 0; x < width; x++) {
        int pixelColor = colorWheelBitmap.getPixel(x, y);
        // Strip alpha channel if your image is opaque
        int pixelColorNoAlpha = pixelColor & 0xFFFFFF;
        int targetColorNoAlpha = targetColor & 0xFFFFFF;
        
        if (pixelColorNoAlpha == targetColorNoAlpha) {
            targetPoint = new Point(x, y);
            break; // Stop at first match, or remove to find all instances
        }
    }
    if (targetPoint != null) break;
}

Color Match with Tolerance (For Anti-Aliased Wheels): #

Most color wheels use anti-aliasing, so exact matches are rare. Use a tolerance threshold to find similar colors:

int targetColor = Color.parseColor("#6DFFE0");
int targetR = Color.red(targetColor);
int targetG = Color.green(targetColor);
int targetB = Color.blue(targetColor);
int tolerance = 10; // Adjust this value based on your image's anti-aliasing

Point targetPoint = null;

for (int y = 0; y < height; y++) {
    for (int x = 0; x < width; x++) {
        int pixelColor = colorWheelBitmap.getPixel(x, y);
        int pixelR = Color.red(pixelColor);
        int pixelG = Color.green(pixelColor);
        int pixelB = Color.blue(pixelColor);
        
        // Check if RGB values fall within the tolerance range
        if (Math.abs(pixelR - targetR) <= tolerance &&
            Math.abs(pixelG - targetG) <= tolerance &&
            Math.abs(pixelB - targetB) <= tolerance) {
            targetPoint = new Point(x, y);
            break;
        }
    }
    if (targetPoint != null) break;
}

Step 3: Move the Indicator to the Found Coordinates #

Once you have the target X/Y coordinates, adjust them to center your indicator (like an ImageView) over the color, then move it:

ImageView indicatorIv = findViewById(R.id.color_indicator);

if (targetPoint != null) {
    // Offset coordinates to center the indicator over the color
    int indicatorX = targetPoint.x - (indicatorIv.getWidth() / 2);
    int indicatorY = targetPoint.y - (indicatorIv.getHeight() / 2);
    
    // Move the indicator
    indicatorIv.setX(indicatorX);
    indicatorIv.setY(indicatorY);
} else {
    // Handle case where the color wasn't found
    Toast.makeText(this, "Target color not found in color wheel", Toast.LENGTH_SHORT).show();
}

Key Tips for Smooth Operation #

• Memory Management: Recycle the bitmap when you’re done to avoid memory leaks:

  if (!colorWheelBitmap.isRecycled()) {
      colorWheelBitmap.recycle();
  }
  

• Multiple Matches: If your color wheel has multiple instances of the target color, calculate the distance from the wheel’s center for each match and pick the closest one.
• Performance: For large images, scan only the circular area of the color wheel instead of the entire rectangle to speed up the process.

内容的提问来源于stack exchange，提问作者Dinesh Raturi