英文:
How do I write pixel data to PNG using stb_image in plain C?
问题
I am wondering how to write RGB pixel data to a PNG using the stb_image library?
我想知道如何使用stb_image库将RGB像素数据写入PNG文件？
I'm trying to write a uint8_t array that contains all the data.
我尝试写入一个包含所有数据的uint8_t数组。
I start with pixel data for 160x60 and up-scale to 1280x480.
我从160x60的像素数据开始，然后放大到1280x480。
I have made a test code that should make a grey PNG but the image is just random noise.
我已经编写了一个测试代码，应该生成一个灰度PNG图像，但图像只是随机噪音。
英文:
I am wondering how to write RGB pixel data to a PNG using the stb_image library?
I'm trying to write a uint8_t array that contains all the data.
I start with pixel data for 160x60 and up-scale to 1280x480.
I have made a test code that should make a grey PNG but the image is just random noise.
#include <stdio.h>#include <stdlib.h>#include <string.h>#include <stdint.h>#include <stdbool.h>#define STB_IMAGE_IMPLEMENTATION#include "stb_image.h"#define STB_IMAGE_WRITE_IMPLEMENTATION#include "stb_image_write.h"void zFill(char * dest, int num, int amount) // fills string with zeros{char str [10];sprintf(str, "%d", num);int len = 0;while (len < amount - strlen(str)){strncat(dest, "0", 2);len++;}strncat(dest, str, strlen(str));}void save_frame(int frame, uint8_t * data) // Saves image{char file[20];sprintf(file, "output/");zFill(file, frame, 6);strncat(file, ".png", 5);printf("%s\n", file);uint8_t image[1280 * 480 * 3]; // output image is upscales 8xint a = 0, b = 0;for (int y = 0; y < 60; y++){for (int x = 0; x < 160; x++){for (int add_b = 0; add_b < 8; add_b++){for (int add_a = 0; add_a < 8; add_a++){image[(a + add_a) * (b + add_b) * 1] = data[x * y * 1];image[(a + add_a) * (b + add_b) * 2] = data[x * y * 2];image[(a + add_a) * (b + add_b) * 3] = data[x * y * 3];}}a = a + 8;}a = 0;b = b + 8;}stbi_write_png(file, 1280, 480, 3, image, 1280 * 3);}int main(){uint8_t image_data[160 * 60 * 3];for (int y = 0; y < 60; y++){for (int x = 0; x < 160; x++){image_data[x * y *1] = 128;image_data[x * y *2] = 128;image_data[x * y *3] = 128;}}save_frame(1, image_data);return 0;}
This is the result:
答案1
得分: 0
问题出在数学计算和放大代码上。
修复：image_data[3 * (y * 160 + x) + 2] = 128; 并移除放大代码。
#include <stdio.h>#include <stdlib.h>#include <string.h>#include <stdint.h>#define STB_IMAGE_IMPLEMENTATION#include "stb_image.h"#define STB_IMAGE_WRITE_IMPLEMENTATION#include "stb_image_write.h"void save_frame(int frame, uint8_t * data) // 保存图像{char file[PATH_MAX];sprintf (file, "output/%06d.png", frame);stbi_write_png(file, 160, 60, 3, data, 160 * 3);}int main(){uint8_t image_data[160 * 60 * 3];for (int y = 0; y < 60; y++){for (int x = 0; x < 160; x++){image_data[3 * (y * 160 + x)] = 128;image_data[3 * (y * 160 + x) + 1] = 128;image_data[3 * (y * 160 + x) + 2] = 128;}}save_frame(1, image_data);return 0;}
英文:
The issue was incorrect math and something with the up-scaling code.
Fix: image_data[3 * (y * 160 + x) + 2] = 128; plus removed up-scaling code.
#include <stdio.h>#include <stdlib.h>#include <string.h>#include <stdint.h>#define STB_IMAGE_IMPLEMENTATION#include "stb_image.h"#define STB_IMAGE_WRITE_IMPLEMENTATION#include "stb_image_write.h"void save_frame(int frame, uint8_t * data) // Saves image{char file[PATH_MAX];sprintf (file, "output/%06d.png", frame);stbi_write_png(file, 160, 60, 3, data, 160 * 3);}int main(){uint8_t image_data[160 * 60 * 3];for (int y = 0; y < 60; y++){for (int x = 0; x < 160; x++){image_data[3 * (y * 160 + x)] = 128;image_data[3 * (y * 160 + x) + 1] = 128;image_data[3 * (y * 160 + x) + 2] = 128;}}save_frame(1, image_data);return 0;}
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