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encode and write PNG to memory (std::vector) with libpng on C++
#include <png.h>
#include <vector>
#include <iostream>
#include <stdlib.h>
//encode and write PNG to memory (std::vector) with libpng on C++
typedef unsigned char ui8;
#define ASSERT_EX(cond, error_message) do { if (!(cond)) { std::cerr << error_message; exit(1);} } while(0)
static void PngWriteCallback(png_structp png_ptr, png_bytep data, png_size_t length) {
std::vector<ui8> *p = (std::vector<ui8>*)png_get_io_ptr(png_ptr);
p->insert(p->end(), data, data + length);
}
struct TPngDestructor {
png_struct *p;
TPngDestructor(png_struct *p) : p(p) {}
~TPngDestructor() { if (p) { png_destroy_write_struct(&p, NULL); } }
};
void WritePngToMemory(size_t w, size_t h, const ui8 *dataRGBA, std::vector<ui8> *out) {
out->clear();
png_structp p = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
ASSERT_EX(p, "png_create_write_struct() failed");
TPngDestructor destroyPng(p);
png_infop info_ptr = png_create_info_struct(p);
ASSERT_EX(info_ptr, "png_create_info_struct() failed");
ASSERT_EX(0 == setjmp(png_jmpbuf(p)), "setjmp(png_jmpbuf(p) failed");
png_set_IHDR(p, info_ptr, w, h, 8,
PNG_COLOR_TYPE_RGBA,
PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_DEFAULT,
PNG_FILTER_TYPE_DEFAULT);
//png_set_compression_level(p, 1);
std::vector<ui8*> rows(h);
for (size_t y = 0; y < h; ++y)
rows[y] = (ui8*)dataRGBA + y * w * 4;
png_set_rows(p, info_ptr, &rows[0]);
png_set_write_fn(p, out, PngWriteCallback, NULL);
png_write_png(p, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
}
@shreyasck

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shreyasck commented Jan 24, 2018

hi, I'm new to libpng
I saw this code very useful for my current requirement
I want to save this in the memory heap. so how can I use this code to save it .

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