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dwebp: add support for BMP output

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Supports alpha output too.

Change-Id: I42ea0bf7b6bbb420f0e537d372a3b13fe00528a9
This commit is contained in:
Pascal Massimino 2013-04-09 18:51:59 -07:00
parent ff885bfe1f
commit b66caee410
3 changed files with 84 additions and 5 deletions
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5
README
View File

@ -247,9 +247,10 @@ Decodes the WebP image file to PNG format [Default]
Use following options to convert into alternate image formats:
-pam ......... save the raw RGBA samples as a color PAM
-ppm ......... save the raw RGB samples as a color PPM
-bmp ......... save as uncompressed BMP format
-pgm ......... save the raw YUV samples as a grayscale PGM
file with IMC4 layout.
-yuv ......... save the raw YUV samples in flat layout.
file with IMC4 layout
-yuv ......... save the raw YUV samples in flat layout
Other options are:
-version .... print version number and exit.

79
examples/dwebp.c
View File

@ -62,6 +62,7 @@ typedef enum {
PAM,
PPM,
PGM,
BMP,
YUV,
ALPHA_PLANE_ONLY // this is for experimenting only
} OutputFileFormat;
@ -225,6 +226,72 @@ static int WritePPM(FILE* fout, const WebPDecBuffer* const buffer, int alpha) {
return 1;
}
static void PutLE16(uint8_t* const dst, uint32_t value) {
dst[0] = (value >> 0) & 0xff;
dst[1] = (value >> 8) & 0xff;
}
static void PutLE32(uint8_t* const dst, uint32_t value) {
PutLE16(dst + 0, (value >> 0) & 0xffff);
PutLE16(dst + 2, (value >> 16) & 0xffff);
}
#define BMP_HEADER_SIZE 54
static int WriteBMP(FILE* fout, const WebPDecBuffer* const buffer) {
const int has_alpha = (buffer->colorspace != MODE_BGR);
const uint32_t width = buffer->width;
const uint32_t height = buffer->height;
const uint8_t* const rgba = buffer->u.RGBA.rgba;
const int stride = buffer->u.RGBA.stride;
const size_t bytes_per_px = has_alpha ? 4 : 3;
uint32_t y;
const int line_size = bytes_per_px * width;
const int bmp_stride = (line_size + 3) & ~3; // pad to 4
const uint32_t total_size = bmp_stride * height + BMP_HEADER_SIZE;
uint8_t bmp_header[BMP_HEADER_SIZE] = { 0 };
// bitmap file header
PutLE16(bmp_header + 0, 0x4d42); // signature 'BM'
PutLE32(bmp_header + 2, total_size); // size including header
PutLE32(bmp_header + 6, 0); // reserved
PutLE32(bmp_header + 10, BMP_HEADER_SIZE); // offset to pixel array
// bitmap info header
PutLE32(bmp_header + 14, 40); // DIB header size
PutLE32(bmp_header + 18, width); // dimensions
PutLE32(bmp_header + 22, -(int)height); // vertical flip!
PutLE16(bmp_header + 26, 1); // number of planes
PutLE16(bmp_header + 28, bytes_per_px * 8); // bits per pixel
PutLE32(bmp_header + 30, 0); // no compression (BI_RGB)
PutLE32(bmp_header + 34, 0); // image size (dummy)
PutLE32(bmp_header + 38, 2400); // x pixels/meter
PutLE32(bmp_header + 42, 2400); // y pixels/meter
PutLE32(bmp_header + 46, 0); // number of palette colors
PutLE32(bmp_header + 50, 0); // important color count
// TODO(skal): color profile
// write header
if (fwrite(bmp_header, sizeof(bmp_header), 1, fout) != 1) {
return 0;
}
// write pixel array
for (y = 0; y < height; ++y) {
if (fwrite(rgba + y * stride, line_size, 1, fout) != 1) {
return 0;
}
// write padding zeroes
if (bmp_stride != line_size) {
const uint8_t zeroes[3] = { 0 };
if (fwrite(zeroes, bmp_stride - line_size, 1, fout) != 1) {
return 0;
}
}
}
return 1;
}
#undef BMP_HEADER_SIZE
static int WriteAlphaPlane(FILE* fout, const WebPDecBuffer* const buffer) {
const uint32_t width = buffer->width;
const uint32_t height = buffer->height;
@ -320,6 +387,8 @@ static void SaveOutput(const WebPDecBuffer* const buffer,
ok &= WritePPM(fout, buffer, 1);
} else if (format == PPM) {
ok &= WritePPM(fout, buffer, 0);
} else if (format == BMP) {
ok &= WriteBMP(fout, buffer);
} else if (format == PGM || format == YUV) {
ok &= WritePGMOrYUV(fout, buffer, format);
} else if (format == ALPHA_PLANE_ONLY) {
@ -345,9 +414,10 @@ static void Help(void) {
"Use following options to convert into alternate image formats:\n"
" -pam ......... save the raw RGBA samples as a color PAM\n"
" -ppm ......... save the raw RGB samples as a color PPM\n"
" -bmp ......... save as uncompressed BMP format\n"
" -pgm ......... save the raw YUV samples as a grayscale PGM\n"
" file with IMC4 layout.\n"
" -yuv ......... save the raw YUV samples in flat layout.\n"
" file with IMC4 layout\n"
" -yuv ......... save the raw YUV samples in flat layout\n"
"\n"
" Other options are:\n"
" -version .... print version number and exit.\n"
@ -401,6 +471,8 @@ int main(int argc, const char *argv[]) {
format = PAM;
} else if (!strcmp(argv[c], "-ppm")) {
format = PPM;
} else if (!strcmp(argv[c], "-bmp")) {
format = BMP;
} else if (!strcmp(argv[c], "-version")) {
const int version = WebPGetDecoderVersion();
printf("%d.%d.%d\n",
@ -481,6 +553,9 @@ int main(int argc, const char *argv[]) {
case PPM:
output_buffer->colorspace = MODE_RGB; // drops alpha for PPM
break;
case BMP:
output_buffer->colorspace = bitstream->has_alpha ? MODE_BGRA : MODE_BGR;
break;
case PGM:
case YUV:
output_buffer->colorspace = bitstream->has_alpha ? MODE_YUVA : MODE_YUV;

5
man/dwebp.1
View File

@ -1,5 +1,5 @@
.\" Hey, EMACS: -*- nroff -*-
.TH DWEBP 1 "February 01, 2013"
.TH DWEBP 1 "April 09, 2013"
.SH NAME
dwebp \- decompress a WebP file to an image file
.SH SYNOPSIS
@ -24,6 +24,9 @@ Print the version number (as major.minor.revision) and exit.
.BI \-o " string
Specify the name of the output file (as PNG format by default).
.TP
.B \-bmp
Change the output format to uncompressed BMP.
.TP
.B \-pam
Change the output format to PAM (retains alpha).
.TP