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stb_image_write can flip images vertically

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This commit is contained in:
Sean Barrett 2018-01-29 02:52:49 -08:00
parent e371bd83f2
commit b056850ea9
1 changed files with 35 additions and 9 deletions
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44
stb_image_write.h
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@ -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)