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vcom5s: implement finger detection

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Uses thresholding of average pixel intensity of the center region of
the image.

Also document guessed meanings of magic numbers for registers.
This commit is contained in:
Daniel Drake 2008-03-20 15:31:03 +00:00
parent d6d4e56ccf
commit 981f2eb0aa
1 changed files with 72 additions and 13 deletions
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85
libfprint/drivers/vcom5s.c
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@ -20,8 +20,10 @@
#define FP_COMPONENT "vcom5s"
/* TODO:
* finger presence detection
* calibration?
* image size: windows gets 300x300 through vpas enrollment util?
* (probably just increase bulk read size?)
* powerdown? does windows do anything special on exit?
*/
#include <errno.h>
@ -51,6 +53,29 @@ struct v5s_dev {
gboolean deactivating;
};
enum v5s_regs {
/* when using gain 0x29:
* a value of 0x00 produces mostly-black image
* 0x09 destroys ridges (too white)
* 0x01 or 0x02 seem good values */
REG_CONTRAST = 0x02,
/* when using contrast 0x01:
* a value of 0x00 will produce an all-black image.
* 0x29 produces a good contrast image: ridges quite dark, but some
* light grey noise as background
* 0x46 produces all-white image with grey ridges (not very dark) */
REG_GAIN = 0x03,
};
enum v5s_cmd {
/* scan one row. has parameter, at a guess this is which row to scan? */
CMD_SCAN_ONE_ROW = 0xc0,
/* scan whole image */
CMD_SCAN = 0xc1,
};
/***** REGISTER I/O *****/
static void sm_write_reg_cb(struct libusb_transfer *transfer)
@ -131,6 +156,41 @@ static void sm_exec_cmd(struct fpi_ssm *ssm, unsigned char cmd,
}
}
/***** FINGER DETECTION *****/
/* We take 64x64 pixels at the center of the image, determine the average
* pixel intensity, and threshold it. */
#define DETBOX_ROW_START 111
#define DETBOX_COL_START 117
#define DETBOX_ROWS 64
#define DETBOX_COLS 64
#define DETBOX_ROW_END (DETBOX_ROW_START + DETBOX_ROWS)
#define DETBOX_COL_END (DETBOX_COL_START + DETBOX_COLS)
#define FINGER_PRESENCE_THRESHOLD 100
static gboolean finger_is_present(unsigned char *data)
{
int row;
uint16_t imgavg = 0;
for (row = DETBOX_ROW_START; row < DETBOX_ROW_END; row++) {
unsigned char *rowdata = data + (row * IMG_WIDTH);
uint16_t rowavg = 0;
int col;
for (col = DETBOX_COL_START; col < DETBOX_COL_END; col++)
rowavg += rowdata[col];
rowavg /= DETBOX_COLS;
imgavg += rowavg;
}
imgavg /= DETBOX_ROWS;
fp_dbg("img avg %d", imgavg);
return (imgavg <= FINGER_PRESENCE_THRESHOLD);
}
/***** IMAGE ACQUISITION *****/
static void capture_iterate(struct fpi_ssm *ssm);
@ -153,9 +213,8 @@ static void capture_cb(struct libusb_transfer *transfer)
* supposed to be handing off this image */
vdev->capture_img = NULL;
fpi_imgdev_report_finger_status(dev, TRUE);
fpi_imgdev_report_finger_status(dev, finger_is_present(img->data));
fpi_imgdev_image_captured(dev, img);
fpi_imgdev_report_finger_status(dev, FALSE);
fpi_ssm_next_state(ssm);
} else {
capture_iterate(ssm);
@ -204,9 +263,9 @@ static void sm_do_capture(struct fpi_ssm *ssm)
/***** CAPTURE LOOP *****/
enum loop_states {
LOOP_WR02,
LOOP_WR03,
LOOP_CMDC1,
LOOP_SET_CONTRAST,
LOOP_SET_GAIN,
LOOP_CMD_SCAN,
LOOP_CAPTURE,
LOOP_CAPTURE_DONE,
LOOP_NUM_STATES,
@ -218,24 +277,24 @@ static void loop_run_state(struct fpi_ssm *ssm)
struct v5s_dev *vdev = dev->priv;
switch (ssm->cur_state) {
case LOOP_WR02:
sm_write_reg(ssm, 0x02, 0x02);
case LOOP_SET_CONTRAST:
sm_write_reg(ssm, REG_CONTRAST, 0x01);
break;
case LOOP_WR03:
sm_write_reg(ssm, 0x03, 0x29);
case LOOP_SET_GAIN:
sm_write_reg(ssm, REG_GAIN, 0x29);
break;
case LOOP_CMDC1:
case LOOP_CMD_SCAN:
if (vdev->deactivating) {
fp_dbg("deactivating, marking completed");
fpi_ssm_mark_completed(ssm);
} else
sm_exec_cmd(ssm, 0xc1, 0x00);
sm_exec_cmd(ssm, CMD_SCAN, 0x00);
break;
case LOOP_CAPTURE:
sm_do_capture(ssm);
break;
case LOOP_CAPTURE_DONE:
fpi_ssm_jump_to_state(ssm, LOOP_CMDC1);
fpi_ssm_jump_to_state(ssm, LOOP_CMD_SCAN);
break;
}
}