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Example code on how to write a bitmap file from scratch.
#include <cstdint> // for specific size integers
#include <fstream> // for file handling
using namespace std;
struct BmpHeader {
char bitmapSignatureBytes[2] = {'B', 'M'};
uint32_t sizeOfBitmapFile = 54 + 786432; // total size of bitmap file
uint32_t reservedBytes = 0;
uint32_t pixelDataOffset = 54;
} bmpHeader;
struct BmpInfoHeader {
uint32_t sizeOfThisHeader = 40;
int32_t width = 512; // in pixels
int32_t height = 512; // in pixels
uint16_t numberOfColorPlanes = 1; // must be 1
uint16_t colorDepth = 24;
uint32_t compressionMethod = 0;
uint32_t rawBitmapDataSize = 0; // generally ignored
int32_t horizontalResolution = 3780; // in pixel per meter
int32_t verticalResolution = 3780; // in pixel per meter
uint32_t colorTableEntries = 0;
uint32_t importantColors = 0;
} bmpInfoHeader;
struct Pixel {
uint8_t blue = 255;
uint8_t green = 255;
uint8_t red = 0;
} pixel;
int main(int argc, char **argv) {
ofstream fout("output.bmp", ios::binary);
fout.write((char *) &bmpHeader, 14);
fout.write((char *) &bmpInfoHeader, 40);
// writing pixel data
size_t numberOfPixels = bmpInfoHeader.width * bmpInfoHeader.height;
for (int i = 0; i < numberOfPixels; i++) {
fout.write((char *) &pixel, 3);
}
fout.close();
return 0;
}
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