1. JavaのBitmap型を
C言語でいじる
@tishibas

2. agenda
● What’s you need
● Code
○ Java side
○ C side
■ parameter
■ include
■ main
● main
○ check
○ lock
○ processing
○ unlock

3. What’s you need
● Android SDK
● Android NDK

4. Java side
public native void func(Bitmap bitmap);
※今回のBitmapのoption→ARGB_8888
他にRGB565とかある

5. Android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := hoge
LOCAL_SRC_FILES := hoge.c
LOCAL_LDLIBS := -llog -ljnigraphics
include $(BUILD_SHARED_LIBRARY)

6. hoge.c include
#include <jni.h>
#include <android/log.h>
#include <android/bitmap.h>

7. hoge.c rgba_8888
typedef struct {
uint8_t red;
uint8_t green;
uint8_t blue;
uint8_t alpha;
} rgba;

8. hoge.c
JNIEXPORT void JNICALL Java_jp_...
_func(
JNIEnv * env,
jobject obj,
jobject jbitmap
)

9. hoge.c parameter
AndroidBitmapInfo info;
void* pixels;
int ret;
int y;
int x;

10. hoge.c check
if ((ret = AndroidBitmap_getInfo(env, jbitmap, &info))
< 0){
return;
}
if (info.format !=
ANDROID_BITMAP_FORMAT_RGBA_8888){
return;
}

11. hoge.c lock
if ((ret = AndroidBitmap_lockPixels(env, jbitmap,
&pixels)) < 0) {
return;
}

12. hoge.c processing
for (y = 0; y < info.height ; y++) {
rgba * line = (rgba *) pixels;
for (x = 0; x < info.width; x++) {
//uint8_t hogehoge = 0.3 * line[x].red
// + 0.59 * line[x].green
// + 0.11*line[x].blue
}
pixels = (char *)pixels + info.stride;
}

13. hoge.h unlock
AndroidBitmap_unlockPixels(env, bitmap);

14. agenda again
● What’s you need
● Code
○ Java side
○ C side
■ parameter
■ include
■ main
● main
○ check
○ lock
○ processing
○ unlock

15. Thank you