feat(chat-character-image): 캐릭터 이미지

- 등록시 블러 이미지를 생성하여 저장하는 기능 추가

src/main/kotlin/kr/co/vividnext/sodalive/utils/ImageBlurUtil.kt

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+package kr.co.vividnext.sodalive.utils
+
+import java.awt.image.BufferedImage
+import kotlin.math.exp
+import kotlin.math.max
+import kotlin.math.min
+
+/**
+ * 가우시안 커널 기반 블러 유틸리티
+ * - 반경(radius)에 따라 커널 크기(2*radius+1) 생성
+ * - 시그마는 관례적으로 radius/3.0 적용
+ * - 수평/수직 분리 합성곱으로 품질과 성능 확보
+ */
+object ImageBlurUtil {
+    fun blur(src: BufferedImage, radius: Int = 10): BufferedImage {
+        require(radius > 0) { "radius must be > 0" }
+        val w = src.width
+        val h = src.height
+        val dst = BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB)
+
+        // 가우시안 1D 커널 생성 및 정규화
+        val sigma = radius / 3.0
+        val kernel = gaussianKernel(radius, sigma)
+
+        // 중간 버퍼
+        val temp = BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB)
+
+        // 수평 합성곱
+        for (y in 0 until h) {
+            for (x in 0 until w) {
+                var aAcc = 0.0
+                var rAcc = 0.0
+                var gAcc = 0.0
+                var bAcc = 0.0
+                for (k in -radius..radius) {
+                    val xx = clamp(x + k, 0, w - 1)
+                    val rgb = src.getRGB(xx, y)
+                    val a = (rgb ushr 24) and 0xFF
+                    val r = (rgb ushr 16) and 0xFF
+                    val g = (rgb ushr 8) and 0xFF
+                    val b = rgb and 0xFF
+                    val wgt = kernel[k + radius]
+                    aAcc += a * wgt
+                    rAcc += r * wgt
+                    gAcc += g * wgt
+                    bAcc += b * wgt
+                }
+                val a = aAcc.toInt().coerceIn(0, 255)
+                val r = rAcc.toInt().coerceIn(0, 255)
+                val g = gAcc.toInt().coerceIn(0, 255)
+                val b = bAcc.toInt().coerceIn(0, 255)
+                temp.setRGB(x, y, (a shl 24) or (r shl 16) or (g shl 8) or b)
+            }
+        }
+
+        // 수직 합성곱
+        for (x in 0 until w) {
+            for (y in 0 until h) {
+                var aAcc = 0.0
+                var rAcc = 0.0
+                var gAcc = 0.0
+                var bAcc = 0.0
+                for (k in -radius..radius) {
+                    val yy = clamp(y + k, 0, h - 1)
+                    val rgb = temp.getRGB(x, yy)
+                    val a = (rgb ushr 24) and 0xFF
+                    val r = (rgb ushr 16) and 0xFF
+                    val g = (rgb ushr 8) and 0xFF
+                    val b = rgb and 0xFF
+                    val wgt = kernel[k + radius]
+                    aAcc += a * wgt
+                    rAcc += r * wgt
+                    gAcc += g * wgt
+                    bAcc += b * wgt
+                }
+                val a = aAcc.toInt().coerceIn(0, 255)
+                val r = rAcc.toInt().coerceIn(0, 255)
+                val g = gAcc.toInt().coerceIn(0, 255)
+                val b = bAcc.toInt().coerceIn(0, 255)
+                dst.setRGB(x, y, (a shl 24) or (r shl 16) or (g shl 8) or b)
+            }
+        }
+        return dst
+    }
+
+    private fun gaussianKernel(radius: Int, sigma: Double): DoubleArray {
+        val size = 2 * radius + 1
+        val kernel = DoubleArray(size)
+        val sigma2 = 2.0 * sigma * sigma
+        var sum = 0.0
+        for (i in -radius..radius) {
+            val v = exp(-(i * i) / sigma2)
+            kernel[i + radius] = v
+            sum += v
+        }
+        // 정규화
+        for (i in kernel.indices) kernel[i] /= sum
+        return kernel
+    }
+
+    private fun clamp(v: Int, lo: Int, hi: Int): Int = max(lo, min(hi, v))
+}