285 lines
9.5 KiB
C
285 lines
9.5 KiB
C
/*
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* wjh_BMP.c
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*
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* Created on: 2024年7月25日
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* Author: wu
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*/
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#include "wjh_BMP.h"
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// BMP 头文件
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typedef struct {
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unsigned char header[100];
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unsigned int width;
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unsigned int height;
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unsigned short bits_per_pixel;
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unsigned int data_offset;
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unsigned int data_size;
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} BMPHeader;
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// 从 BMP 数据中提取头信息
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static void parse_bmp_header(unsigned char *bmp_data, BMPHeader *header) {
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u32 offset = bmp_data[13];
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offset = offset * 256 + bmp_data[12];
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offset = offset * 256 + bmp_data[11];
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offset = offset * 256 + bmp_data[10];
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memcpy(header->header, bmp_data, offset);
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header->width = bmp_data[21];
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header->width = header->width * 256 + bmp_data[20];
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header->width = header->width * 256 + bmp_data[19];
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header->width = header->width * 256 + bmp_data[18];
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header->height = bmp_data[25];
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header->height = header->height * 256 + bmp_data[24];
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header->height = header->height * 256 + bmp_data[23];
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header->height = header->height * 256 + bmp_data[22];
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header->bits_per_pixel = bmp_data[29];
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header->bits_per_pixel = header->bits_per_pixel * 256 + bmp_data[28];
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header->data_offset = offset;
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header->data_size = bmp_data[37];
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header->data_size = header->data_size * 256 + bmp_data[36];
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header->data_size = header->data_size * 256 + bmp_data[35];
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header->data_size = header->data_size * 256 + bmp_data[34];
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}
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// 从 BMP 数据中提取头信息
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static void Set_bmp_header(u8 *scaled_data,u32 new_width,u32 new_height,u32 total) {
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scaled_data[18] = new_width % 256;
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new_width /= 256;
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scaled_data[19] = new_width % 256;
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new_width /= 256;
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scaled_data[20] = new_width % 256;
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new_width /= 256;
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scaled_data[21] = new_width % 256;
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scaled_data[22] = new_height % 256;
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new_height /= 256;
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scaled_data[23] = new_height % 256;
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new_height /= 256;
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scaled_data[24] = new_height % 256;
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new_height /= 256;
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scaled_data[25] = new_height % 256;
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scaled_data[34] = total % 256;
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total /= 256;
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scaled_data[35] = total % 256;
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total /= 256;
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scaled_data[36] = total % 256;
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total /= 256;
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scaled_data[37] = total % 256;
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}
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// 获取像素数据
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static unsigned short get_pixel(unsigned char *data, int x, int y, int width,int bits_per_pixel) {
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int index = y * width + x;
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if (bits_per_pixel == 24) {
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// 24位BMP
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return ((unsigned short *)data)[index];
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} else if (bits_per_pixel == 16) {
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// 16位R5G6B5 BMP
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unsigned short color;
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color = data[index * 2]; // 蓝色
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color |= (data[index * 2 + 1] << 8); // 绿色
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return color;
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} else {
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// 未知位深
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return 0;
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}
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}
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// 设置像素数据
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static void set_pixel(unsigned char *data, int x, int y, int width, int bits_per_pixel, unsigned short color) {
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int index = y * width + x;
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if (bits_per_pixel == 24) {
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// 24位BMP
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((unsigned short *)data)[index] = color;
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} else if (bits_per_pixel == 16) {
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// 16位R5G6B5 BMP
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data[index * 2] = color; // 蓝色
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data[index * 2 + 1] = color >> 8; // 绿色
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} else {
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// 未知位深
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return;
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}
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}
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// 线性插值函数
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static unsigned short interpolate(unsigned short a, unsigned short b, float t) {
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unsigned short red = ((a >> 11) & 0x1F) * (1 - t) + ((b >> 11) & 0x1F) * t;
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unsigned short green = ((a >> 5) & 0x3F) * (1 - t) + ((b >> 5) & 0x3F) * t;
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unsigned short blue = (a & 0x1F) * (1 - t) + (b & 0x1F) * t;
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return (red << 11) | (green << 5) | blue;
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}
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// 图像缩放
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static void scale_image_ByEqualRatio(unsigned char *src, unsigned char *dst, BMPHeader *header, float scale) {
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int new_width = header->width * scale;
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int new_height = header->height * scale;
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int y;
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for (y = 0; y < new_height; y++) {
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int x;
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for (x = 0; x < new_width; x++) {
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float src_x = x / scale;
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float src_y = y / scale;
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int x0 = (int)src_x;
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int y0 = (int)src_y;
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int x1 = x0 + 1;
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int y1 = y0 + 1;
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if (x1 >= header->width) x1 = header->width - 1;
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if (y1 >= header->height) y1 = header->height - 1;
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unsigned short p0 = get_pixel(src, x0, y0, header->width,header->bits_per_pixel);
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unsigned short p1 = get_pixel(src, x1, y0, header->width,header->bits_per_pixel);
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unsigned short p2 = get_pixel(src, x0, y1, header->width,header->bits_per_pixel);
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unsigned short p3 = get_pixel(src, x1, y1, header->width,header->bits_per_pixel);
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float tx = src_x - x0;
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float ty = src_y - y0;
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unsigned short interpolated_pixel = interpolate(
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interpolate(p0, p1, tx),
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interpolate(p2, p3, tx),
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ty
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);
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set_pixel(dst, x, y, new_width,header->bits_per_pixel, interpolated_pixel);
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}
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}
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}
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u8* BMP_Scale_Change_ByEqualRatio(u8 *bmp_data,float scale) {
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BMPHeader header;
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parse_bmp_header(bmp_data, &header);
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int new_width = header.width * scale;
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int new_height = header.height * scale;
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return BMP_Scale_Change(bmp_data,new_width,new_height);
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// unsigned char *scaled_data = (unsigned char *)malloc(new_width * new_height * 2 + 54);
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//
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// for(u32 i = 0;i < 54;i ++){
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// scaled_data[i] = header.header[i];
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// }
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//
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// scale_image_ByEqualRatio(bmp_data + header.data_offset, scaled_data + 54, &header, scale);
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//
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// // 更新 BMP 头信息
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// Set_bmp_header(scaled_data,new_width,new_height,new_width * new_height * 2);
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//
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// return scaled_data;
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}
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// 图像缩放
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static void scale_image(unsigned char *src, unsigned char *dst, BMPHeader *header, int new_width, int new_height) {
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int y;
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for (y = 0; y < new_height; y++) {
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int x;
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for (x = 0; x < new_width; x++) {
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//算出新的这个左边颜色应该通过原图哪个位置的坐标颜色进行计算
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float src_x = (float)x * header->width / new_width;
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float src_y = (float)y * header->height / new_height;
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int x0 = (int)src_x;//原图对应格子x轴
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int y0 = (int)src_y;//原图对应格子y轴
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int x1 = x0 + 1;//找四个格子进行算法扩张，所以找到下一个格子坐标
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int y1 = y0 + 1;
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//如果格子超了范围，则用当前格子
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if (x1 >= header->width) x1 = header->width - 1;
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if (y1 >= header->height) y1 = header->height - 1;
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//获取四个格子的RGB值
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unsigned short p0 = get_pixel(src, x0, y0, header->width,header->bits_per_pixel);
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unsigned short p1 = get_pixel(src, x1, y0, header->width,header->bits_per_pixel);
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unsigned short p2 = get_pixel(src, x0, y1, header->width,header->bits_per_pixel);
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unsigned short p3 = get_pixel(src, x1, y1, header->width,header->bits_per_pixel);
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//算法
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float tx = src_x - x0;
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float ty = src_y - y0;
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unsigned short interpolated_pixel = interpolate(
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interpolate(p0, p1, tx),//算出x轴对应的两个格子的中间值
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interpolate(p2, p3, tx),//算出x轴对应的两个格子的中间值
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ty
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);//算出y轴对应的两个格子的中间值
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set_pixel(dst, x, y, new_width,header->bits_per_pixel, interpolated_pixel);
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}
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}
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}
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// 对齐每一行数据到4字节边界
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void align_row(unsigned char *row, int width, int bytes_per_pixel) {
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// int padding = (4 - (width * bytes_per_pixel % 4)) % 4;
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// for (int i = 0; i < padding; ++i) {
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// row[width + i] = 0xFF;
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// }
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int padding = (4 - (width % 4)) % 4;
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for (int i = 0; i < padding; ++i) {
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row[width + i] = row[width + i - 2];
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}
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}
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//----BMP图根据宽高进行拉伸或缩小-------------------------------------------------------------
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//描述: 将目标bmp_data数组拉伸或缩小至width和heigh大小
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//参数：bmp_data：图片数据 new_width：目标宽度 new_height：目标高度
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//返回：等比缩放后的bmp图片数据（需要自行释放！！！！！！！！）
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//------------------------------------------------------------------------------
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u8* BMP_Scale_Change(u8 *bmp_data,u32 new_width,u32 new_height){
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BMPHeader header;
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parse_bmp_header(bmp_data, &header);
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// 计算每行需要的填充字节
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int stride = header.width * 2; // 每个像素2字节
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int padding = (4 - (stride % 4)) % 4; // 计算填充字节
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stride += padding; // 添加填充字节
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header.width = stride / 2;
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unsigned char *aligned_data = NULL;
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if(padding != 0){
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// 创建一个新的图像数据数组，包括填充字节
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aligned_data = (unsigned char *)malloc(header.height * (header.width + stride) * 2);
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for (int y = 0; y < header.height; ++y) {
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memcpy(aligned_data + y * stride, bmp_data + header.data_offset + y * header.width * 2, header.width * 2);
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align_row(aligned_data + y * stride, header.width * 2, 2);
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}
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}
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unsigned char *scaled_data = (unsigned char *)malloc(new_width * new_height * 2 + header.data_offset);
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for(u32 i = 0;i < header.data_offset;i ++){
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scaled_data[i] = header.header[i];
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}
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//不需要拉伸
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if(header.width == new_width&&header.height == new_height){
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memcpy(scaled_data + header.data_offset,padding?aligned_data:(bmp_data + header.data_offset),new_width * new_height * 2);
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}else{
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scale_image(padding?aligned_data:(bmp_data + header.data_offset), scaled_data + header.data_offset, &header, new_width, new_height);
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}
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// scale_image(padding?aligned_data:(bmp_data + header.data_offset), scaled_data + header.data_offset, &header, new_width, new_height);
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if(aligned_data != NULL){
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free(aligned_data);
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}
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// 更新 BMP 头信息
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Set_bmp_header(scaled_data,new_width,new_height,new_width * new_height * 2);
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return scaled_data;
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}
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