// Computes the DENORMS for bl(baseline) and cn(character) normalization
// during feature extraction. The input denorm describes the current state
// of the blob, which is usually a baseline-normalized word.
// The Transforms setup are as follows:
// Baseline Normalized (bl) Output:
// We center the grapheme by aligning the x-coordinate of its centroid with
// x=128 and leaving the already-baseline-normalized y as-is.
//
// Character Normalized (cn) Output:
// We align the grapheme's centroid at the origin and scale it
// asymmetrically in x and y so that the 2nd moments are a standard value
// (51.2) ie the result is vaguely square.
// If classify_nonlinear_norm is true:
// A non-linear normalization is setup that attempts to evenly distribute
// edges across x and y.
//
// Some of the fields of fx_info are also setup:
// Length: Total length of outline.
// Rx: Rounded y second moment. (Reversed by convention.)
// Ry: rounded x second moment.
// Xmean: Rounded x center of mass of the blob.
// Ymean: Rounded y center of mass of the blob.
void Classify::SetupBLCNDenorms(const TBLOB& blob, bool nonlinear_norm,
DENORM* bl_denorm, DENORM* cn_denorm,
INT_FX_RESULT_STRUCT* fx_info) {
// Compute 1st and 2nd moments of the original outline.
FCOORD center, second_moments;
int length = blob.ComputeMoments(¢er, &second_moments);
if (fx_info != nullptr) {
fx_info->Length = length;
fx_info->Rx = IntCastRounded(second_moments.y());
fx_info->Ry = IntCastRounded(second_moments.x());
fx_info->Xmean = IntCastRounded(center.x());
fx_info->Ymean = IntCastRounded(center.y());
}
// Setup the denorm for Baseline normalization.
bl_denorm->SetupNormalization(nullptr, nullptr, &blob.denorm(), center.x(), 128.0f,
1.0f, 1.0f, 128.0f, 128.0f);
// Setup the denorm for character normalization.
if (nonlinear_norm) {
GenericVector<GenericVector<int> > x_coords;
GenericVector<GenericVector<int> > y_coords;
TBOX box;
blob.GetPreciseBoundingBox(&box);
box.pad(1, 1);
blob.GetEdgeCoords(box, &x_coords, &y_coords);
cn_denorm->SetupNonLinear(&blob.denorm(), box, UINT8_MAX, UINT8_MAX,
0.0f, 0.0f, x_coords, y_coords);
} else {
cn_denorm->SetupNormalization(nullptr, nullptr, &blob.denorm(),
center.x(), center.y(),
51.2f / second_moments.x(),
51.2f / second_moments.y(),
128.0f, 128.0f);
}
}
// Helper gets the image of a rectangle, using the block.re_rotation() if
// needed to get to the image, and rotating the result back to horizontal
// layout. (CJK characters will be on their left sides) The vertical text flag
// is set in the returned ImageData if the text was originally vertical, which
// can be used to invoke a different CJK recognition engine. The revised_box
// is also returned to enable calculation of output bounding boxes.
ImageData* Tesseract::GetRectImage(const TBOX& box, const BLOCK& block,
int padding, TBOX* revised_box) const {
TBOX wbox = box;
wbox.pad(padding, padding);
*revised_box = wbox;
// Number of clockwise 90 degree rotations needed to get back to tesseract
// coords from the clipped image.
int num_rotations = 0;
if (block.re_rotation().y() > 0.0f)
num_rotations = 1;
else if (block.re_rotation().x() < 0.0f)
num_rotations = 2;
else if (block.re_rotation().y() < 0.0f)
num_rotations = 3;
// Handle two cases automatically: 1 the box came from the block, 2 the box
// came from a box file, and refers to the image, which the block may not.
if (block.bounding_box().major_overlap(*revised_box))
revised_box->rotate(block.re_rotation());
// Now revised_box always refers to the image.
// BestPix is never colormapped, but may be of any depth.
Pix* pix = BestPix();
int width = pixGetWidth(pix);
int height = pixGetHeight(pix);
TBOX image_box(0, 0, width, height);
// Clip to image bounds;
*revised_box &= image_box;
if (revised_box->null_box()) return NULL;
Box* clip_box = boxCreate(revised_box->left(), height - revised_box->top(),
revised_box->width(), revised_box->height());
Pix* box_pix = pixClipRectangle(pix, clip_box, NULL);
if (box_pix == NULL) return NULL;
boxDestroy(&clip_box);
if (num_rotations > 0) {
Pix* rot_pix = pixRotateOrth(box_pix, num_rotations);
pixDestroy(&box_pix);
box_pix = rot_pix;
}
// Convert sub-8-bit images to 8 bit.
int depth = pixGetDepth(box_pix);
if (depth < 8) {
Pix* grey;
grey = pixConvertTo8(box_pix, false);
pixDestroy(&box_pix);
box_pix = grey;
}
bool vertical_text = false;
if (num_rotations > 0) {
// Rotated the clipped revised box back to internal coordinates.
FCOORD rotation(block.re_rotation().x(), -block.re_rotation().y());
revised_box->rotate(rotation);
if (num_rotations != 2)
vertical_text = true;
}
return new ImageData(vertical_text, box_pix);
}
