Init commit

app/src/main/cpp/einkdither.cpp

@@ -0,0 +1,89 @@
+#include <jni.h>
+#include <android/bitmap.h>
+#include <android/log.h>
+#include <cstdint>
+#include <cstring>
+#include <algorithm>
+
+#define LOG_TAG "EinkDither"
+#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)
+
+template <typename T>
+static inline T clamp(T val, T minVal, T maxVal) {
+    return (val < minVal) ? minVal : (val > maxVal) ? maxVal : val;
+}
+
+int quantizeTo16Levels(int gray) {
+    return (gray * 15 + 127) / 255 * 17;
+}
+
+extern "C"
+JNIEXPORT jobject JNICALL
+Java_moe_fuquan_einkdither_DitherUtils_applyDithering(JNIEnv *env, jclass clazz, jobject bitmap) {
+    if (bitmap == nullptr) return nullptr;
+
+    AndroidBitmapInfo info;
+    void* pixels = nullptr;
+
+    if (AndroidBitmap_getInfo(env, bitmap, &info) < 0){
+        LOGE("AndroidBitmap_getInfo failed");
+        return bitmap;
+    }
+//    if (info.format != ANDROID_BITMAP_FORMAT_RGBA_8888) return bitmap;
+    if (AndroidBitmap_lockPixels(env, bitmap, &pixels) < 0){
+        LOGE("AndroidBitmap_getInfo failed");
+        return bitmap;
+    }
+
+    int width = info.width;
+    int height = info.height;
+    uint32_t* line = (uint32_t*)pixels;
+
+    // 转换为灰度数组
+    int** gray = new int*[height];
+    for (int y = 0; y < height; y++) {
+        gray[y] = new int[width];
+        for (int x = 0; x < width; x++) {
+            uint32_t pixel = line[y * width + x];
+            int alpha = (pixel >> 24) & 0xFF;
+            int r = (pixel >> 16) & 0xFF;
+            int g = (pixel >> 8) & 0xFF;
+            int b = (pixel) & 0xFF;
+
+            if (alpha == 0)
+                gray[y][x] = -1;
+            else
+                gray[y][x] = (r * 299 + g * 587 + b * 114) / 1000;
+        }
+    }
+
+    // Floyd-Steinberg 抖动
+    for (int y = 0; y < height; y++) {
+        for (int x = 0; x < width; x++) {
+            if (gray[y][x] == -1) {
+                line[y * width + x] = 0x00000000;
+                continue;
+            }
+
+            int oldPixel = gray[y][x];
+            int newPixel = quantizeTo16Levels(oldPixel);
+            int error = oldPixel - newPixel;
+            gray[y][x] = newPixel;
+
+            if (x + 1 < width && gray[y][x + 1] != -1)
+                gray[y][x + 1] = clamp(gray[y][x + 1] + error / 2, 0, 255);
+            if (y + 1 < height && gray[y + 1][x] != -1)
+                gray[y + 1][x] = clamp(gray[y + 1][x] + error / 2, 0, 255);
+
+            uint8_t g = gray[y][x];
+            line[y * width + x] = 0xFF000000 | (g << 16) | (g << 8) | g;
+        }
+    }
+
+    // 清理
+    for (int i = 0; i < height; i++) delete[] gray[i];
+    delete[] gray;
+
+    AndroidBitmap_unlockPixels(env, bitmap);
+    return bitmap;
+}