我正在使用stb库为OpenGL动态加载纹理。我正在尝试使用stb_image_write.h中的函数。我找不到有关如何正确使用功能stbi_write_png_to_mem
的任何文档,我的代码如下所示>
#ifndef STB_IMAGE_WRITE_IMPLEMENTATION #define STB_IMAGE_WRITE_IMPLEMENTATION #include <stb/stb_image_write.h> int main( ) { // data is filled in later in program int size , width , height ; unsigned char* data = ( unsigned char* ) malloc( width * height ) ; ... ... ... // this is where the issue lies stbi_write_png_to_mem( ) ; }
我查看了github,并查看了源代码本身。我在Google上找不到任何东西。我不确定此功能需要什么输入,因为什么都不清楚,这意味着什么。函数的源是
STBIWDEF unsigned char *stbi_write_png_to_mem(const unsigned char *pixels, int stride_bytes, int x, int y, int n, int *out_len) { int force_filter = stbi_write_force_png_filter; int ctype[5] = { -1, 0, 4, 2, 6 }; unsigned char sig[8] = { 137,80,78,71,13,10,26,10 }; unsigned char *out,*o, *filt, *zlib; signed char *line_buffer; int j,zlen; if (stride_bytes == 0) stride_bytes = x * n; if (force_filter >= 5) { force_filter = -1; } filt = (unsigned char *) STBIW_MALLOC((x*n+1) * y); if (!filt) return 0; line_buffer = (signed char *) STBIW_MALLOC(x * n); if (!line_buffer) { STBIW_FREE(filt); return 0; } for (j=0; j < y; ++j) { int filter_type; if (force_filter > -1) { filter_type = force_filter; stbiw__encode_png_line((unsigned char*)(pixels), stride_bytes, x, y, j, n, force_filter, line_buffer); } else { // Estimate the best filter by running through all of them: int best_filter = 0, best_filter_val = 0x7fffffff, est, i; for (filter_type = 0; filter_type < 5; filter_type++) { stbiw__encode_png_line((unsigned char*)(pixels), stride_bytes, x, y, j, n, filter_type, line_buffer); // Estimate the entropy of the line using this filter; the less, the better. est = 0; for (i = 0; i < x*n; ++i) { est += abs((signed char) line_buffer[i]); } if (est < best_filter_val) { best_filter_val = est; best_filter = filter_type; } } if (filter_type != best_filter) { // If the last iteration already got us the best filter, don't redo it stbiw__encode_png_line((unsigned char*)(pixels), stride_bytes, x, y, j, n, best_filter, line_buffer); filter_type = best_filter; } } // when we get here, filter_type contains the filter type, and line_buffer contains the data filt[j*(x*n+1)] = (unsigned char) filter_type; STBIW_MEMMOVE(filt+j*(x*n+1)+1, line_buffer, x*n); } STBIW_FREE(line_buffer); zlib = stbi_zlib_compress(filt, y*( x*n+1), &zlen, stbi_write_png_compression_level); STBIW_FREE(filt); if (!zlib) return 0; // each tag requires 12 bytes of overhead out = (unsigned char *) STBIW_MALLOC(8 + 12+13 + 12+zlen + 12); if (!out) return 0; *out_len = 8 + 12+13 + 12+zlen + 12; o=out; STBIW_MEMMOVE(o,sig,8); o+= 8; stbiw__wp32(o, 13); // header length stbiw__wptag(o, "IHDR"); stbiw__wp32(o, x); stbiw__wp32(o, y); *o++ = 8; *o++ = STBIW_UCHAR(ctype[n]); *o++ = 0; *o++ = 0; *o++ = 0; stbiw__wpcrc(&o,13); stbiw__wp32(o, zlen); stbiw__wptag(o, "IDAT"); STBIW_MEMMOVE(o, zlib, zlen); o += zlen; STBIW_FREE(zlib); stbiw__wpcrc(&o, zlen); stbiw__wp32(o,0); stbiw__wptag(o, "IEND"); stbiw__wpcrc(&o,0); STBIW_ASSERT(o == out + *out_len); return out; }
我的目标是本质上将图片数据输出到内存中的png中,而不是文件中,因此我可以在程序中将其格式化为png格式的其他位置使用它。
我正在使用stb库为OpenGL动态加载纹理。我正在尝试使用stb_image_write.h中的函数。我找不到任何有关如何正确使用此功能的文档...
大多数参数与传递给具有stbi_write_png
的documentation in the header file的参数相同: