java 降低图片清晰度

如果你想在Java中降低图片的清晰度，可以使用以下代码示例：

public Bitmap decreaseImageSharpness(Bitmap src, float radius) {
    // 将Bitmap转换为可修改的像素数组
    int width = src.getWidth();
    int height = src.getHeight();
    int[] pixels = new int[width * height];
    src.getPixels(pixels, 0, width, 0, 0, width, height);

    // 计算卷积核
    int kernelSize = (int) (radius * 2 + 1);
    float[] kernel = new float[kernelSize * kernelSize];
    for (int i = 0; i < kernelSize; i++) {
        for (int j = 0; j < kernelSize; j++) {
            kernel[i * kernelSize + j] = 1.0f / (kernelSize * kernelSize);
        }
    }

    // 对像素数组进行卷积操作
    int[] resultPixels = new int[pixels.length];
    ConvolutionMatrix convMatrix = new ConvolutionMatrix(kernelSize);
    convMatrix.applyConvolution(pixels, resultPixels, width, height, convMatrix);

    // 将修改后的像素数组转换为Bitmap并返回
    Bitmap result = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    result.setPixels(resultPixels, 0, width, 0, 0, width, height);
    return result;
}

以上代码中，使用了一个ConvolutionMatrix类来进行卷积操作。该类的代码示例如下：

public class ConvolutionMatrix {
    private int size;
    private float[] matrix;

    public ConvolutionMatrix(int size) {
        this.size = size;
        this.matrix = new float[size * size];
    }

    public void set(float[] matrix) {
        for (int i = 0; i < size * size; i++) {
            this.matrix[i] = matrix[i];
        }
    }

    public void applyConvolution(int[] pixels, int[] resultPixels, int width, int height, ConvolutionMatrix matrix) {
        int halfSize = (int) Math.floor(matrix.size / 2);
        for (int y = 0; y < height; y++) {
            for (int x = 0; x < width; x++) {
                int index = y * width + x;
                float r = 0, g = 0, b = 0;
                for (int j = -halfSize; j <= halfSize; j++) {
                    for (int i = -halfSize; i <= halfSize; i++) {
                        int pixelIndex = (y + j) * width + (x + i);
                        if (pixelIndex >= 0 && pixelIndex < pixels.length) {
                            int pixel = pixels[pixelIndex];
                            float coeff = matrix.matrix[(j + halfSize) * matrix.size + i + halfSize];
                            r += Color.red(pixel) * coeff;
                            g += Color.green(pixel) * coeff;
                            b += Color.blue(pixel) * coeff;
                        }
                    }
                }
                resultPixels[index] = Color.argb(Color.alpha(pixels[index]), (int) r, (int) g, (int) b);
            }
        }
    }
}

以上代码中，ConvolutionMatrix类的set方法用于设置卷积核，applyConvolution方法用于对像素数组进行卷积操作。在applyConvolution方法中，对于每个像素点，都会计算出一个以该像素点为中心的正方形框，框内像素点的加权平均值作为该像素点的值。最后，将处理后的像素数组生成为一个新的Bitmap并返回。