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Add very basic exposure compensation

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fruchti 2019-11-14 18:50:29 +01:00
parent 1e0daa39cc
commit 91dc86102f
3 changed files with 23 additions and 10 deletions
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2
build-number.txt
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@ -1 +1 @@
499 510

26
src/ov7670.c
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@ -152,9 +152,10 @@ uint8_t ImageBuffer[CAMERA_IMAGE_WIDTH * CAMERA_IMAGE_HEIGHT / 8];
static volatile int CurrentLine = 0; static volatile int CurrentLine = 0;
uint8_t LineBuffer[CAMERA_IMAGE_WIDTH + 40]; uint8_t LineBuffer[CAMERA_IMAGE_WIDTH + 40];
int LineCount = 0; int LineCount = 0;
static int FrameCount = 0; static volatile int FrameCount = 0;
volatile int Camera_Captured = 0; volatile int Camera_Captured = 0;
unsigned int BlackPixels = 0; static unsigned int BlackPixels = 0;
static volatile int ExposureCorrection = 0;
static uint8_t ReadRegister(uint8_t reg) static uint8_t ReadRegister(uint8_t reg)
{ {
@ -311,9 +312,11 @@ void TIM1_CC_IRQHandler(void)
CurrentLine = 0; CurrentLine = 0;
FrameCount++; FrameCount++;
// Correct exposure across frames
ExposureCorrection += 32 * BlackPixels / CAMERA_PIXELS - 16;
// Check if the last frame's exposure is reasonable // Check if the last frame's exposure is reasonable
if(BlackPixels >= (unsigned)(CAMERA_PIXELS * CAMERA_EXPOSURE_LOW) if(FrameCount >= 5)
&& BlackPixels <= (unsigned)(CAMERA_PIXELS * CAMERA_EXPOSURE_HIGH))
{ {
Camera_Captured = 1; Camera_Captured = 1;
// Disable everything // Disable everything
@ -370,6 +373,21 @@ void TIM3_IRQHandler(void)
for(int i = 0; i < CAMERA_IMAGE_WIDTH; i++) for(int i = 0; i < CAMERA_IMAGE_WIDTH; i++)
{ {
int pixel = LineBuffer[i + 15] + x_error; int pixel = LineBuffer[i + 15] + x_error;
if(ExposureCorrection < 0)
{
if(pixel < -ExposureCorrection)
pixel = 0;
else
pixel += ExposureCorrection;
}
else
{
if(pixel > 255 - ExposureCorrection)
pixel = 255;
else
pixel += ExposureCorrection;
}
int line = CurrentLine / 2; int line = CurrentLine / 2;
int error; int error;
if(pixel < 127) if(pixel < 127)

5
src/ov7670.h
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@ -7,11 +7,6 @@
#define CAMERA_IMAGE_HEIGHT 144 #define CAMERA_IMAGE_HEIGHT 144
#define CAMERA_PIXELS (CAMERA_IMAGE_WIDTH * CAMERA_IMAGE_HEIGHT) #define CAMERA_PIXELS (CAMERA_IMAGE_WIDTH * CAMERA_IMAGE_HEIGHT)
// Maximum and minimum share of black pixels for an image to be accepted
#define CAMERA_EXPOSURE_LIMIT 0.4
#define CAMERA_EXPOSURE_LOW (0.5 - CAMERA_EXPOSURE_LIMIT)
#define CAMERA_EXPOSURE_HIGH (0.5 + CAMERA_EXPOSURE_LIMIT)
// Use 2D Floyd-Steinberg dithering. Uncomment to use simple line-wise // Use 2D Floyd-Steinberg dithering. Uncomment to use simple line-wise
// dithering. // dithering.
#define CAMERA_USE_2D_DITHERING #define CAMERA_USE_2D_DITHERING