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-rw-r--r--jni/filters/contrast.c46
1 files changed, 46 insertions, 0 deletions
diff --git a/jni/filters/contrast.c b/jni/filters/contrast.c
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--- /dev/null
+++ b/jni/filters/contrast.c
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+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "filters.h"
+
+unsigned char clamp(int c)
+{
+ int N = 255;
+ c &= ~(c >> 31);
+ c -= N;
+ c &= (c >> 31);
+ c += N;
+ return (unsigned char) c;
+}
+
+void JNIFUNCF(ImageFilterContrast, nativeApplyFilter, jobject bitmap, jint width, jint height, jfloat bright)
+{
+ char* destination = 0;
+ AndroidBitmap_lockPixels(env, bitmap, (void**) &destination);
+ unsigned char * rgb = (unsigned char * )destination;
+ int i;
+ int len = width * height * 4;
+ float m = (float)pow(2, bright/100.);
+ float c = 127-m*127;
+
+ for (i = 0; i < len; i+=4) {
+ rgb[RED] = clamp((int)(m*rgb[RED]+c));
+ rgb[GREEN] = clamp((int)(m*rgb[GREEN]+c));
+ rgb[BLUE] = clamp((int)(m*rgb[BLUE]+c));
+ }
+ AndroidBitmap_unlockPixels(env, bitmap);
+}
+