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stb_image_write: small buffer to avoid calling fwrite on every pixel

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This commit is contained in:
Sean Barrett 2020-07-13 02:20:59 -07:00
parent 802a1df278
commit 523a14f3e1
1 changed files with 40 additions and 16 deletions
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56
stb_image_write.h
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@ -267,6 +267,8 @@ typedef struct
{
stbi_write_func *func;
void *context;
unsigned char buffer[64];
int buf_used;
} stbi__write_context;
// initialize a callback-based context
@ -380,16 +382,36 @@ static void stbiw__writef(stbi__write_context *s, const char *fmt, ...)
va_end(v);
}
static void stbiw__write_flush(stbi__write_context *s)
{
if (s->buf_used) {
s->func(s->context, &s->buffer, s->buf_used);
s->buf_used = 0;
}
}
static void stbiw__putc(stbi__write_context *s, unsigned char c)
{
s->func(s->context, &c, 1);
}
static void stbiw__write1(stbi__write_context *s, unsigned char a)
{
if (s->buf_used + 1 > sizeof(s->buffer))
stbiw__write_flush(s);
s->buffer[s->buf_used++] = a;
}
static void stbiw__write3(stbi__write_context *s, unsigned char a, unsigned char b, unsigned char c)
{
unsigned char arr[3];
arr[0] = a; arr[1] = b; arr[2] = c;
s->func(s->context, arr, 3);
int n;
if (s->buf_used + 3 > sizeof(s->buffer))
stbiw__write_flush(s);
n = s->buf_used;
s->buf_used = n+3;
s->buffer[n+0] = a;
s->buffer[n+1] = b;
s->buffer[n+2] = c;
}
static void stbiw__write_pixel(stbi__write_context *s, int rgb_dir, int comp, int write_alpha, int expand_mono, unsigned char *d)
@ -398,7 +420,7 @@ static void stbiw__write_pixel(stbi__write_context *s, int rgb_dir, int comp, in
int k;
if (write_alpha < 0)
s->func(s->context, &d[comp - 1], 1);
stbiw__write1(s, d[comp - 1]);
switch (comp) {
case 2: // 2 pixels = mono + alpha, alpha is written separately, so same as 1-channel case
@ -406,7 +428,7 @@ static void stbiw__write_pixel(stbi__write_context *s, int rgb_dir, int comp, in
if (expand_mono)
stbiw__write3(s, d[0], d[0], d[0]); // monochrome bmp
else
s->func(s->context, d, 1); // monochrome TGA
stbiw__write1(s, d[0]); // monochrome TGA
break;
case 4:
if (!write_alpha) {
@ -422,7 +444,7 @@ static void stbiw__write_pixel(stbi__write_context *s, int rgb_dir, int comp, in
break;
}
if (write_alpha > 0)
s->func(s->context, &d[comp - 1], 1);
stbiw__write1(s, d[comp - 1]);
}
static void stbiw__write_pixels(stbi__write_context *s, int rgb_dir, int vdir, int x, int y, int comp, void *data, int write_alpha, int scanline_pad, int expand_mono)
@ -447,6 +469,7 @@ static void stbiw__write_pixels(stbi__write_context *s, int rgb_dir, int vdir, i
unsigned char *d = (unsigned char *) data + (j*x+i)*comp;
stbiw__write_pixel(s, rgb_dir, comp, write_alpha, expand_mono, d);
}
stbiw__write_flush(s);
s->func(s->context, &zero, scanline_pad);
}
}
@ -476,7 +499,7 @@ static int stbi_write_bmp_core(stbi__write_context *s, int x, int y, int comp, c
STBIWDEF int stbi_write_bmp_to_func(stbi_write_func *func, void *context, int x, int y, int comp, const void *data)
{
stbi__write_context s;
stbi__write_context s = { 0 };
stbi__start_write_callbacks(&s, func, context);
return stbi_write_bmp_core(&s, x, y, comp, data);
}
@ -484,7 +507,7 @@ STBIWDEF int stbi_write_bmp_to_func(stbi_write_func *func, void *context, int x,
#ifndef STBI_WRITE_NO_STDIO
STBIWDEF int stbi_write_bmp(char const *filename, int x, int y, int comp, const void *data)
{
stbi__write_context s;
stbi__write_context s = { 0 };
if (stbi__start_write_file(&s,filename)) {
int r = stbi_write_bmp_core(&s, x, y, comp, data);
stbi__end_write_file(&s);
@ -557,24 +580,25 @@ static int stbi_write_tga_core(stbi__write_context *s, int x, int y, int comp, v
if (diff) {
unsigned char header = STBIW_UCHAR(len - 1);
s->func(s->context, &header, 1);
stbiw__write1(s, header);
for (k = 0; k < len; ++k) {
stbiw__write_pixel(s, -1, comp, has_alpha, 0, begin + k * comp);
}
} else {
unsigned char header = STBIW_UCHAR(len - 129);
s->func(s->context, &header, 1);
stbiw__write1(s, header);
stbiw__write_pixel(s, -1, comp, has_alpha, 0, begin);
}
}
}
stbiw__write_flush(s);
}
return 1;
}
STBIWDEF int stbi_write_tga_to_func(stbi_write_func *func, void *context, int x, int y, int comp, const void *data)
{
stbi__write_context s;
stbi__write_context s = { 0 };
stbi__start_write_callbacks(&s, func, context);
return stbi_write_tga_core(&s, x, y, comp, (void *) data);
}
@ -582,7 +606,7 @@ STBIWDEF int stbi_write_tga_to_func(stbi_write_func *func, void *context, int x,
#ifndef STBI_WRITE_NO_STDIO
STBIWDEF int stbi_write_tga(char const *filename, int x, int y, int comp, const void *data)
{
stbi__write_context s;
stbi__write_context s = { 0 };
if (stbi__start_write_file(&s,filename)) {
int r = stbi_write_tga_core(&s, x, y, comp, (void *) data);
stbi__end_write_file(&s);
@ -748,7 +772,7 @@ static int stbi_write_hdr_core(stbi__write_context *s, int x, int y, int comp, f
STBIWDEF int stbi_write_hdr_to_func(stbi_write_func *func, void *context, int x, int y, int comp, const float *data)
{
stbi__write_context s;
stbi__write_context s = { 0 };
stbi__start_write_callbacks(&s, func, context);
return stbi_write_hdr_core(&s, x, y, comp, (float *) data);
}
@ -756,7 +780,7 @@ STBIWDEF int stbi_write_hdr_to_func(stbi_write_func *func, void *context, int x,
#ifndef STBI_WRITE_NO_STDIO
STBIWDEF int stbi_write_hdr(char const *filename, int x, int y, int comp, const float *data)
{
stbi__write_context s;
stbi__write_context s = { 0 };
if (stbi__start_write_file(&s,filename)) {
int r = stbi_write_hdr_core(&s, x, y, comp, (float *) data);
stbi__end_write_file(&s);
@ -1552,7 +1576,7 @@ static int stbi_write_jpg_core(stbi__write_context *s, int width, int height, in
STBIWDEF int stbi_write_jpg_to_func(stbi_write_func *func, void *context, int x, int y, int comp, const void *data, int quality)
{
stbi__write_context s;
stbi__write_context s = { 0 };
stbi__start_write_callbacks(&s, func, context);
return stbi_write_jpg_core(&s, x, y, comp, (void *) data, quality);
}
@ -1561,7 +1585,7 @@ STBIWDEF int stbi_write_jpg_to_func(stbi_write_func *func, void *context, int x,
#ifndef STBI_WRITE_NO_STDIO
STBIWDEF int stbi_write_jpg(char const *filename, int x, int y, int comp, const void *data, int quality)
{
stbi__write_context s;
stbi__write_context s = { 0 };
if (stbi__start_write_file(&s,filename)) {
int r = stbi_write_jpg_core(&s, x, y, comp, data, quality);
stbi__end_write_file(&s);