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dwebp: add PAM output support

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retains the alpha channel rather than stripping it as with PPM.

display from ImageMagick can render the files

Change-Id: I4f3a5d332937e0aeaf4e3fbd214fdae3b5382fb8
This commit is contained in:
James Zern 2012-07-20 16:06:06 -07:00
parent c3a207b9f4
commit d919ed06eb
2 changed files with 27 additions and 8 deletions
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26
examples/dwebp.c
View File

@ -59,6 +59,7 @@ extern void* VP8GetCPUInfo; // opaque forward declaration.
// Output types
typedef enum {
PNG = 0,
PAM,
PPM,
PGM,
ALPHA_PLANE_ONLY // this is for experimenting only
@ -201,15 +202,22 @@ static int WritePNG(FILE* out_file, const WebPDecBuffer* const buffer) {
}
#endif
static int WritePPM(FILE* fout, const WebPDecBuffer* const buffer) {
static int WritePPM(FILE* fout, const WebPDecBuffer* const buffer, int alpha) {
const uint32_t width = buffer->width;
const uint32_t height = buffer->height;
const unsigned char* const rgb = buffer->u.RGBA.rgba;
const int stride = buffer->u.RGBA.stride;
const size_t bytes_per_px = alpha ? 4 : 3;
uint32_t y;
fprintf(fout, "P6\n%d %d\n255\n", width, height);
if (alpha) {
fprintf(fout, "P7\nWIDTH %d\nHEIGHT %d\nDEPTH 4\nMAXVAL 255\n"
"TUPLTYPE RGB_ALPHA\nENDHDR\n", width, height);
} else {
fprintf(fout, "P6\n%d %d\n255\n", width, height);
}
for (y = 0; y < height; ++y) {
if (fwrite(rgb + y * stride, width, 3, fout) != 3) {
if (fwrite(rgb + y * stride, width, bytes_per_px, fout) != bytes_per_px) {
return 0;
}
}
@ -289,8 +297,10 @@ static void SaveOutput(const WebPDecBuffer* const buffer,
#else
ok &= WritePNG(fout, buffer);
#endif
} else if (format == PAM) {
ok &= WritePPM(fout, buffer, 1);
} else if (format == PPM) {
ok &= WritePPM(fout, buffer);
ok &= WritePPM(fout, buffer, 0);
} else if (format == PGM) {
ok &= WritePGM(fout, buffer);
} else if (format == ALPHA_PLANE_ONLY) {
@ -314,7 +324,8 @@ static void Help(void) {
printf("Usage: dwebp in_file [options] [-o out_file]\n\n"
"Decodes the WebP image file to PNG format [Default]\n"
"Use following options to convert into alternate image formats:\n"
" -ppm ......... save the raw RGB samples as color PPM\n"
" -pam ......... save the raw RGBA samples as a color PAM\n"
" -ppm ......... save the raw RGB samples as a color PPM\n"
" -pgm ......... save the raw YUV samples as a grayscale PGM\n"
" file with IMC4 layout.\n"
" Other options are:\n"
@ -367,6 +378,8 @@ int main(int argc, const char *argv[]) {
config.options.no_fancy_upsampling = 1;
} else if (!strcmp(argv[c], "-nofilter")) {
config.options.bypass_filtering = 1;
} else if (!strcmp(argv[c], "-pam")) {
format = PAM;
} else if (!strcmp(argv[c], "-ppm")) {
format = PPM;
} else if (!strcmp(argv[c], "-version")) {
@ -434,6 +447,9 @@ int main(int argc, const char *argv[]) {
output_buffer->colorspace = bitstream->has_alpha ? MODE_RGBA : MODE_RGB;
#endif
break;
case PAM:
output_buffer->colorspace = MODE_RGBA;
break;
case PPM:
output_buffer->colorspace = MODE_RGB; // drops alpha for PPM
break;

9
man/dwebp.1
View File

@ -1,5 +1,5 @@
.\" Hey, EMACS: -*- nroff -*-
.TH DWEBP 1 "January 24, 2012"
.TH DWEBP 1 "July 20, 2012"
.SH NAME
dwebp \- decompress a WebP file to an image file
.SH SYNOPSIS
@ -11,7 +11,7 @@ This manual page documents the
.B dwebp
command.
.PP
\fBdwebp\fP decompresses WebP files into PNG, PPM or PGM images.
\fBdwebp\fP decompresses WebP files into PNG, PAM, PPM or PGM images.
.SH OPTIONS
The basic options are:
.TP
@ -24,8 +24,11 @@ Print the version number (as major.minor.revision) and exit.
.B \-o string
Specify the name of the output file (as PNG format by default).
.TP
.B \-pam
Change the output format to PAM (retains alpha).
.TP
.B \-ppm
Change the output format to PPM.
Change the output format to PPM (discards alpha).
.TP
.B \-pgm
Change the output format to PGM. The output consist of luma/chroma