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#include <stdio.h>

#include <stdlib.h>

#include <string.h>

// A simple structure to store ARGB data

typedef struct {

    unsigned char a; // alpha channel

    unsigned char r; // red channel

    unsigned char g; // green channel

    unsigned char b; // blue channel

} argb_t;

// A simple function to print ARGB data in hexadecimal format

void print_argb(argb_t *data, size_t size) {

    for (size_t i = 0; i < size; i++) {

        printf("%02X%02X%02X%02X ", data[i].a, data[i].r, data[i].g, data[i].b);

        if ((i + 1) % 10 == 0) printf("\n");

    }

}

// A simple function to compress ARGB data using run-length encoding (RLE)

// RLE is a lossless compression algorithm that replaces consecutive identical bytes with a count and a byte value

// For example: FFFFFFFF FFFFFFFF FFFFFFFF -> 03 FF

// The compressed data is stored in a buffer and its size is returned as an output parameter

unsigned char *compress_argb(argb_t *data, size_t size, size_t *out_size) {

    // Allocate a buffer to store the compressed data

    // The worst case scenario is that the compressed data is twice as large as the original data

    unsigned char *buffer = malloc(size * 2);

    if (buffer == NULL) return NULL;

    // Initialize some variables for the compression loop

    size_t index = 0; // the index of the current byte in the original data

    size_t count = 0; // the count of consecutive identical bytes in the original data

    unsigned char value = 0; // the value of the current byte in the original data

    // Loop through the original data and compress it using RLE

    while (index < size * sizeof(argb_t)) {

        // Get the current byte value from the original data

        value = ((unsigned char *)data)[index];

        // Count how many consecutive identical bytes there are from this position onwards

        count = 1;

        while (index + count < size * sizeof(argb_t) && ((unsigned char *)data)[index + count] == value) {

            count++;

        }

        // Write the count and the value to the buffer as two bytes

        buffer[*out_size] = (unsigned char)count;

        buffer[*out_size + 1] = value;

        // Increment the output size by two bytes

        *out_size += 2;

        // Increment the index by the count of identical bytes

        index += count;

    }

    return buffer;

}

// A simple function to decompress ARGB data using run-length encoding (RLE)

// RLE is a lossless compression algorithm that replaces a count and a byte value with consecutive identical bytes

// For example: 03 FF -> FFFFFFFF FFFFFFFF FFFFFFFF

// The decompressed data is stored in a buffer and its size is returned as an output parameter

argb_t *decompress_argb(unsigned char *data, size_t size, size_t *out_size) {

   

   // Allocate a buffer to store the decompressed data

   // The worst case scenario is that the decompressed data is half as large as the compressed data

   argb_t *buffer = malloc(size / 2);

   if (buffer == NULL) return NULL;

   // Initialize some variables for the decompression loop

   size_t index = 0; //the index of the current byte in the compressed data

   size_t count = 0; //the count of consecutive identical bytes in the decompressed data

   unsigned char value = 0; //the value of each identical byte in the decompressed data

// Loop through the compressed data and decompress it using RLE

   while (index < size) {

       // Get the count and the value from the compressed data as two bytes

       count = (size_t)data[index];

       value = data[index + 1];

       // Write the count of identical bytes to the buffer with the same value

       memset(((unsigned char *)buffer) + *out_size, value, count);

       // Increment the output size by the count of identical bytes

       *out_size += count;

       // Increment the index by two bytes

       index += 2;

   }

   return buffer;

}

// A simple function to test the compression and decompression functions

void test_argb() {

    // Create some sample ARGB data

    argb_t sample[] = {

        {0xFF, 0xFF, 0xFF, 0xFF}, // white

        {0xFF, 0x00, 0x00, 0x00}, // black

        {0xFF, 0xFF, 0x00, 0x00}, // red

        {0xFF, 0x00, 0xFF, 0x00}, // green

        {0xFF, 0x00, 0x00, 0xFF}, // blue

        {0xFF, 0xC8, 0xC8, 0xC8}, // gray

        {0xFF, 0xC8, 0xC8, 0xC8}, // gray

        {0xFF, 0xC8, 0xC8, 0xC8}, // gray

        {0xFF, 0x00, 0x00, 0xFF}, // blue

        {0xFF, 0x00, 0x00, 0xFF}, // blue

        {0xFF, 0x00, 0x00, 0xFF}, // blue

    };

    // Print the original data

    printf("Original data:\n");

    print_argb(sample, sizeof(sample) / sizeof(argb_t));

    printf("\n");

    // Compress the data using RLE

    size_t compressed_size = 0;

    unsigned char *compressed_data = compress_argb(sample,

                                                   sizeof(sample) / sizeof(argb_t),

                                                   &compressed_size);

    // Print the compressed data in hexadecimal format

    printf("Compressed data:\n");

    for (size_t i = 0; i < compressed_size; i++) {

        printf("%02X ", compressed_data[i]);

        if ((i + 1) % 10 == 0) printf("\n");

    }

    printf("\n");

    // Decompress the data using RLE

    size_t decompressed_size = 0;

argb_t *decompressed_data = decompress_argb(compressed_data,

                                                 compressed_size,

                                                 &decompressed_size);

    // Print the decompressed data

    printf("Decompressed data:\n");

    print_argb(decompressed_data, decompressed_size / sizeof(argb_t));

    printf("\n");

    // Free the allocated memory

    free(compressed_data);

    free(decompressed_data);

}

// The main function to run the test

int main() {

    test_argb();

    return 0;

}

__EOF__

本文作者：LhTian
本文链接：https://www.cnblogs.com/LhTian/p/17214275.html
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