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98 lines
2.6 KiB
98 lines
2.6 KiB
2 months ago
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/*
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* Image Library -- Detection of textured images
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*
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* (c) 2006 Pavel Charvat <pchar@ucw.cz>
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*
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* This software may be freely distributed and used according to the terms
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* of the GNU Lesser General Public License.
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*/
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#undef LOCAL_DEBUG
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#include <ucw/lib.h>
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#include <images/images.h>
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#include <images/signature.h>
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#include <images/math.h>
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#include <string.h>
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#define MAX_CELLS_COLS 4
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#define MAX_CELLS_ROWS 4
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void
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image_sig_detect_textured(struct image_sig_data *data)
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{
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if (image_sig_textured_threshold <= 0)
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{
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DBG("Zero textured threshold.");
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return;
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}
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uint cols = data->cols;
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uint rows = data->rows;
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uint cell_cols = MIN((cols + 1) / 2, MAX_CELLS_COLS);
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uint cell_rows = MIN((rows + 1) / 2, MAX_CELLS_ROWS);
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uint cell_x[MAX_CELLS_COLS + 1];
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uint cell_y[MAX_CELLS_ROWS + 1];
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uint i, j;
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u32 cnt[IMAGE_REG_MAX];
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if (cell_cols * cell_rows < 4)
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{
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DBG("Image is not textured.");
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return;
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}
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DBG("Detecting textured image... cols=%u rows=%u cell_cols=%u cell_rows=%u", cols, rows, cell_cols, cell_rows);
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/* Compute cells boundaries */
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for (i = 1, j = 0; i < cell_cols; i++)
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cell_x[i] = fast_div_u32_u8(j += cols, cell_cols);
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cell_x[0] = 0;
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cell_x[cell_cols] = cols;
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for (i = 1, j = 0; i < cell_rows; i++)
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cell_y[i] = fast_div_u32_u8(j += rows, cell_rows);
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cell_y[0] = 0;
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cell_y[cell_rows] = rows;
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/* Preprocess blocks */
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for (uint i = 0; i < data->regions_count; i++)
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for (struct image_sig_block *block = data->regions[i].blocks; block; block = block->next)
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block->region = i;
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/* Process cells */
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double e = 0;
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for (uint j = 0; j < cell_rows; j++)
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for (uint i = 0; i < cell_cols; i++)
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{
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uint cell_area = 0;
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bzero(cnt, data->regions_count * sizeof(u32));
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struct image_sig_block *b1 = data->blocks + cell_x[i] + cell_y[j] * cols, *b2;
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for (uint y = cell_y[j]; y < cell_y[j + 1]; y++, b1 += cols)
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{
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b2 = b1;
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for (uint x = cell_x[i]; x < cell_x[i + 1]; x++, b2++)
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{
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cnt[b2->region]++;
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cell_area++;
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}
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}
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for (uint k = 0; k < data->regions_count; k++)
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{
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int a = data->blocks_count * cnt[k] - cell_area * data->regions[k].count;
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e += (double)a * a / ((double)isqr(data->regions[k].count) * cell_area);
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}
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}
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DBG("Coefficient=%g", (double)e / (data->regions_count * data->blocks_count));
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/* Threshold */
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if (e < image_sig_textured_threshold * data->regions_count * data->blocks_count)
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{
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data->flags |= IMAGE_SIG_TEXTURED;
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DBG("Image is textured.");
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}
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else
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DBG("Image is not textured.");
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}
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