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fix binary data writing #7

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fix binary data writing #7

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41c5b51
fix binary format writing
weanti Sep 16, 2025
10684ac
formatting
weanti Sep 16, 2025
3b9bbf8
fix 2 byte writing
weanti Sep 16, 2025
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163 changes: 98 additions & 65 deletions src/pnmio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,40 @@
#define GREYSCALE_TYPE 0 /* used for PFM */
#define RGB_TYPE 1 /* used for PFM */

void write_ascii( FILE *f, int *img_out, int x_scaled_size, int y_scaled_size, int linevals )
{
for ( int i = 0; i < x_scaled_size * y_scaled_size; ++i )
{
fprintf(f, "%d ", img_out[i]);
if ( i % linevals == linevals-1 )
fprintf(f, "\n");
}
}
// the unit of information is 1 byte. used for 8 bit grayscale and 24 bit rgb components
void write_binary_1( FILE *f, int *img_out, int x_scaled_size, int y_scaled_size )
{
char c;
for ( int i = 0; i < x_scaled_size * y_scaled_size; ++i )
{
c = (char)img_out[i];
fwrite(&c, sizeof(char), 1, f );
}
}
// the unit of information is 2 bytes. used for 16 bit grayscale and 48 bit rgb components
void write_binary_2( FILE *f, int *img_out, int x_scaled_size, int y_scaled_size)
{
char upper;
char lower;
short s;
for ( int i = 0; i < x_scaled_size * y_scaled_size; ++i )
{
s = (short)img_out[i];
upper = s >> 8;
lower = s & 0xFF;
fwrite(&upper, sizeof(char), 1, f );
fwrite(&lower, sizeof(char), 1, f );
}
}

/* get_pnm_type:
* Read the header contents of a PBM/PGM/PPM/PFM file up to the point of
Expand Down Expand Up @@ -482,40 +516,40 @@ void write_pbm_file(FILE *f, int *img_out,
int x_size, int y_size, int x_scale_val, int y_scale_val, int linevals,
int is_ascii)
{
int i, j, x_scaled_size, y_scaled_size;
int k, v, temp, step;
x_scaled_size = x_size * x_scale_val;
y_scaled_size = y_size * y_scale_val;
/* Write the magic number string. */
if (is_ascii == 1) {
fprintf(f, "P1\n");
step = 1;
} else {
fprintf(f, "P4\n");
step = 8;
}
/* Write the image dimensions. */
fprintf(f, "%d %d\n", x_scaled_size, y_scaled_size);
/* Write the image data. */
for (i = 0; i < y_scaled_size; i++) {
for (j = 0; j < x_scaled_size; j+=step) {
if (is_ascii == 1) {
fprintf(f, "%d ", img_out[i*x_scaled_size+j]);
} else {
temp = 0;
for (k = 0; k < 8; k++) {
v = img_out[i*x_scaled_size+j+k];
temp |= (v << (7-k));
}
fprintf(f, "%c", temp);
}
if (((i*x_scaled_size+j) % linevals) == (linevals-1)) {
fprintf(f, "\n");
}
}
}
int i, j, x_scaled_size, y_scaled_size;
int k, v, temp, step;

x_scaled_size = x_size * x_scale_val;
y_scaled_size = y_size * y_scale_val;
/* Write the magic number string. */
if (is_ascii == 1) {
fprintf(f, "P1\n");
step = 1;
} else {
fprintf(f, "P4\n");
step = 8;
}
/* Write the image dimensions. */
fprintf(f, "%d %d\n", x_scaled_size, y_scaled_size);

/* Write the image data. */
for (i = 0; i < y_scaled_size; i++) {
for (j = 0; j < x_scaled_size; j+=step) {
if (is_ascii == 1) {
fprintf(f, "%d ", img_out[i*x_scaled_size+j]);
} else {
temp = 0;
for (k = 0; k < 8; k++) {
v = img_out[i*x_scaled_size+j+k];
temp |= (v << (7-k));
}
fprintf(f, "%c", temp);
}
if (((i*x_scaled_size+j) % linevals) == (linevals-1)) {
fprintf(f, "\n");
}
}
}
}

/* write_pgm_file:
Expand All @@ -525,7 +559,7 @@ void write_pgm_file(FILE *f, int *img_out,
int x_size, int y_size, int x_scale_val, int y_scale_val,
int img_colors, int linevals, int is_ascii)
{
int i, j, x_scaled_size, y_scaled_size;
int x_scaled_size, y_scaled_size;

x_scaled_size = x_size * x_scale_val;
y_scaled_size = y_size * y_scale_val;
Expand All @@ -541,18 +575,21 @@ void write_pgm_file(FILE *f, int *img_out,
fprintf(f, "%d\n", img_colors);

/* Write the image data. */
for (i = 0; i < y_scaled_size; i++) {
for (j = 0; j < x_scaled_size; j++) {
if (is_ascii == 1) {
fprintf(f, "%d ", img_out[i*x_scaled_size+j]);
if (((i*x_scaled_size+j) % linevals) == (linevals-1)) {
fprintf(f, "\n");
}
} else {
fprintf(f, "%c", img_out[i*x_scaled_size+j]);
}
if ( is_ascii )
{
write_ascii(f, img_out, x_scaled_size, y_scaled_size, linevals );
}
else
{
if ( img_colors < 256 )
{
write_binary_1(f, img_out, x_scaled_size, y_scaled_size);
}
}
else
{
write_binary_2(f, img_out, x_scaled_size, y_scaled_size);
}
}
}

/* write_ppm_file:
Expand All @@ -562,7 +599,7 @@ void write_ppm_file(FILE *f, int *img_out,
int x_size, int y_size, int x_scale_val, int y_scale_val,
int img_colors, int is_ascii)
{
int i, j, x_scaled_size, y_scaled_size;
int x_scaled_size, y_scaled_size;

x_scaled_size = x_size * x_scale_val;
y_scaled_size = y_size * y_scale_val;
Expand All @@ -576,24 +613,20 @@ void write_ppm_file(FILE *f, int *img_out,
fprintf(f, "%d %d\n", x_scaled_size, y_scaled_size);
/* Write the maximum color/grey level allowed. */
fprintf(f, "%d\n", img_colors);

/* Write the image data. */
for (i = 0; i < y_scaled_size; i++) {
for (j = 0; j < x_scaled_size; j++) {
if (is_ascii == 1) {
fprintf(f, "%d %d %d ",
img_out[3*(i*x_scaled_size+j)+0],
img_out[3*(i*x_scaled_size+j)+1],
img_out[3*(i*x_scaled_size+j)+2]);
if ((j % 4) == 0) {
fprintf(f, "\n");
}
} else {
fprintf(f, "%c%c%c",
img_out[3*(i*x_scaled_size+j)+0],
img_out[3*(i*x_scaled_size+j)+1],
img_out[3*(i*x_scaled_size+j)+2]);
}

if ( is_ascii )
{
write_ascii(f, img_out, x_scaled_size, y_scaled_size*3, x_scaled_size*3 );
}
else
{
if ( img_colors < 256 )
{
write_binary_1(f, img_out, x_scaled_size, y_scaled_size*3);
}
else
{
write_binary_2(f, img_out, x_scaled_size, y_scaled_size*3);
}
}
}
Expand Down