From b056850ea9118b69325d973f8aef7f843527e299 Mon Sep 17 00:00:00 2001 From: Sean Barrett Date: Mon, 29 Jan 2018 02:52:49 -0800 Subject: [PATCH] stb_image_write can flip images vertically --- stb_image_write.h | 44 +++++++++++++++++++++++++++++++++++--------- 1 file changed, 35 insertions(+), 9 deletions(-) diff --git a/stb_image_write.h b/stb_image_write.h index 9d553e0..94c4cf9 100644 --- a/stb_image_write.h +++ b/stb_image_write.h @@ -1,4 +1,4 @@ -/* stb_image_write - v1.07 - public domain - http://nothings.org/stb/stb_image_write.h +/* stb_image_write - v1.08 - public domain - http://nothings.org/stb/stb_image_write.h writes out PNG/BMP/TGA/JPEG/HDR images to C stdio - Sean Barrett 2010-2015 no warranty implied; use at your own risk @@ -29,7 +29,7 @@ BUILDING: USAGE: - There are four functions, one for each image file format: + There are five functions, one for each image file format: int stbi_write_png(char const *filename, int w, int h, int comp, const void *data, int stride_in_bytes); int stbi_write_bmp(char const *filename, int w, int h, int comp, const void *data); @@ -37,7 +37,9 @@ USAGE: int stbi_write_hdr(char const *filename, int w, int h, int comp, const float *data); int stbi_write_jpg(char const *filename, int w, int h, int comp, const float *data); - There are also four equivalent functions that use an arbitrary write function. You are + void stbi_flip_vertically_on_write(int flag); // flag is non-zero to flip data vertically + + There are also five equivalent functions that use an arbitrary write function. You are expected to open/close your file-equivalent before and after calling these: int stbi_write_png_to_func(stbi_write_func *func, void *context, int w, int h, int comp, const void *data, int stride_in_bytes); @@ -151,6 +153,8 @@ STBIWDEF int stbi_write_tga_to_func(stbi_write_func *func, void *context, int w, STBIWDEF int stbi_write_hdr_to_func(stbi_write_func *func, void *context, int w, int h, int comp, const float *data); STBIWDEF int stbi_write_jpg_to_func(stbi_write_func *func, void *context, int x, int y, int comp, const void *data, int quality); +extern void stbi_flip_vertically_on_write(int flip_boolean); + #ifdef __cplusplus } #endif @@ -208,6 +212,13 @@ STBIWDEF int stbi_write_jpg_to_func(stbi_write_func *func, void *context, int x, #define STBIW_UCHAR(x) (unsigned char) ((x) & 0xff) +int stbi__flip_vertically_on_write=0; + +void stbi_flip_vertically_on_write(int flag) +{ + stbi__flip_vertically_on_write = flag; +} + typedef struct { stbi_write_func *func; @@ -341,6 +352,9 @@ static void stbiw__write_pixels(stbi__write_context *s, int rgb_dir, int vdir, i if (y <= 0) return; + if (stbi__flip_vertically_on_write) + vdir *= -1; + if (vdir < 0) j_end = -1, j = y-1; else @@ -412,11 +426,21 @@ static int stbi_write_tga_core(stbi__write_context *s, int x, int y, int comp, v "111 221 2222 11", 0, 0, format, 0, 0, 0, 0, 0, x, y, (colorbytes + has_alpha) * 8, has_alpha * 8); } else { int i,j,k; + int jend, jdir; stbiw__writef(s, "111 221 2222 11", 0,0,format+8, 0,0,0, 0,0,x,y, (colorbytes + has_alpha) * 8, has_alpha * 8); - for (j = y - 1; j >= 0; --j) { - unsigned char *row = (unsigned char *) data + j * x * comp; + if (stbi__flip_vertically_on_write) { + j = 0; + jend = y; + jdir = 1; + } else { + j = y-1; + jend = -1; + jdir = -1; + } + for (; j != jend; j += jdir) { + unsigned char *row = (unsigned char *) data + j * x * comp; int len; for (i = 0; i < x; i += len) { @@ -630,7 +654,7 @@ static int stbi_write_hdr_core(stbi__write_context *s, int x, int y, int comp, f s->func(s->context, buffer, len); for(i=0; i < y; i++) - stbiw__write_hdr_scanline(s, x, comp, scratch, data + comp*i*x); + stbiw__write_hdr_scanline(s, x, comp, scratch, data + comp*x*(stbi__flip_vertically_on_write ? y-1-i : i)*x); STBIW_FREE(scratch); return 1; } @@ -932,7 +956,7 @@ unsigned char *stbi_write_png_to_mem(unsigned char *pixels, int stride_bytes, in for (p=0; p < 2; ++p) { for (k= p?best:0; k < 5; ++k) { // @TODO: clarity: rewrite this to go 0..5, and 'continue' the unwanted ones during 2nd pass int type = mymap[k],est=0; - unsigned char *z = pixels + stride_bytes*j; + unsigned char *z = pixels + stride_bytes*(stbi__flip_vertically_on_write ? y-1-j : j); for (i=0; i < n; ++i) switch (type) { case 0: line_buffer[i] = z[i]; break; @@ -954,7 +978,7 @@ unsigned char *stbi_write_png_to_mem(unsigned char *pixels, int stride_bytes, in case 6: line_buffer[i] = z[i] - stbiw__paeth(z[i-n], 0,0); break; } } - if (p) break; + if (p != 0) break; for (i=0; i < x*n; ++i) est += abs((signed char) line_buffer[i]); if (est < bestval) { bestval = est; best = k; } @@ -1318,7 +1342,7 @@ static int stbi_write_jpg_core(stbi__write_context *s, int width, int height, in float YDU[64], UDU[64], VDU[64]; for(row = y, pos = 0; row < y+8; ++row) { for(col = x; col < x+8; ++col, ++pos) { - int p = row*width*comp + col*comp; + int p = (stbi__flip_vertically_on_write ? height-1-row : row)*width*comp + col*comp; float r, g, b; if(row >= height) { p -= width*comp*(row+1 - height); @@ -1377,6 +1401,8 @@ STBIWDEF int stbi_write_jpg(char const *filename, int x, int y, int comp, const #endif // STB_IMAGE_WRITE_IMPLEMENTATION /* Revision history + 1.08 (2018-01-29) + add stbi__flip_vertically_on_write 1.07 (2017-07-24) doc fix 1.06 (2017-07-23)