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Make rescaler methods generic

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to be used in rescaling of lossless bitstreams.
(cherry picked from commit 2e12a3045498b6faf13b93bc25391e8226119f0a)
This commit is contained in:
Urvang Joshi
2012-03-21 06:48:50 +00:00
committed by James Zern
parent 3eacee8158
commit efc2016a31
3 changed files with 45 additions and 34 deletions
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48
src/dec/webp.c
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@ -610,7 +610,7 @@ VP8StatusCode WebPDecode(const uint8_t* data, uint32_t data_size,
}
//------------------------------------------------------------------------------
// Simple picture rescaler
// Cropping & rescaling.
int WebPIoInitFromOptions(const WebPDecoderOptions* const options,
VP8Io* const io) {
@ -665,12 +665,12 @@ int WebPIoInitFromOptions(const WebPDecoderOptions* const options,
}
#define RFIX 30
#define MULT(x,y) (((int64_t)(x) * (y) + (1 << (RFIX - 1))) >> RFIX)
#define MULT_FIX(x,y) (((int64_t)(x) * (y) + (1 << (RFIX - 1))) >> RFIX)
void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height,
uint8_t* dst, int dst_width, int dst_height,
int dst_stride, int x_add, int x_sub, int y_add,
int y_sub, int32_t* work) {
uint8_t* const dst, int dst_width, int dst_height,
int dst_stride, int num_channels, int x_add, int x_sub,
int y_add, int y_sub, int32_t* const work) {
wrk->x_expand = (src_width < dst_width);
wrk->src_width = src_width;
wrk->src_height = src_height;
@ -678,6 +678,7 @@ void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height,
wrk->dst_height = dst_height;
wrk->dst = dst;
wrk->dst_stride = dst_stride;
wrk->num_channels = num_channels;
// for 'x_expand', we use bilinear interpolation
wrk->x_add = wrk->x_expand ? (x_sub - 1) : x_add - x_sub;
wrk->x_sub = wrk->x_expand ? (x_add - 1) : x_sub;
@ -690,34 +691,40 @@ void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height,
((int64_t)dst_height << RFIX) / (x_sub * src_height) :
((int64_t)dst_height << RFIX) / (x_add * src_height);
wrk->irow = work;
wrk->frow = work + dst_width;
wrk->frow = work + num_channels * dst_width;
}
void WebPRescalerImportRow(const uint8_t* const src, WebPRescaler* const wrk) {
int x_in = 0;
void WebPRescalerImportRow(const uint8_t* const src, int channel,
WebPRescaler* const wrk) {
const int x_stride = wrk->num_channels;
const int x_out_max = wrk->dst_width * wrk->num_channels;
int x_in = channel;
int x_out;
int accum = 0;
if (!wrk->x_expand) {
int sum = 0;
for (x_out = 0; x_out < wrk->dst_width; ++x_out) {
for (x_out = channel; x_out < x_out_max; x_out += x_stride) {
accum += wrk->x_add;
for (; accum > 0; accum -= wrk->x_sub) {
sum += src[x_in++];
sum += src[x_in];
x_in += x_stride;
}
{ // Emit next horizontal pixel.
const int32_t base = src[x_in++];
const int32_t base = src[x_in];
const int32_t frac = base * (-accum);
x_in += x_stride;
wrk->frow[x_out] = (sum + base) * wrk->x_sub - frac;
// fresh fractional start for next pixel
sum = (int)MULT(frac, wrk->fx_scale);
sum = (int)MULT_FIX(frac, wrk->fx_scale);
}
}
} else { // simple bilinear interpolation
int left = src[0], right = src[0];
for (x_out = 0; x_out < wrk->dst_width; ++x_out) {
int left = src[channel], right = src[channel];
for (x_out = channel; x_out < x_out_max; x_out += x_stride) {
if (accum < 0) {
left = right;
right = src[++x_in];
x_in += x_stride;
right = src[x_in];
accum += wrk->x_add;
}
wrk->frow[x_out] = right * wrk->x_add + (left - right) * accum;
@ -725,7 +732,7 @@ void WebPRescalerImportRow(const uint8_t* const src, WebPRescaler* const wrk) {
}
}
// Accumulate the new row's contribution
for (x_out = 0; x_out < wrk->dst_width; ++x_out) {
for (x_out = channel; x_out < x_out_max; x_out += x_stride) {
wrk->irow[x_out] += wrk->frow[x_out];
}
}
@ -733,10 +740,11 @@ void WebPRescalerImportRow(const uint8_t* const src, WebPRescaler* const wrk) {
void WebPRescalerExportRow(WebPRescaler* const wrk) {
int x_out;
const int yscale = wrk->fy_scale * (-wrk->y_accum);
const int x_out_max = wrk->dst_width * wrk->num_channels;
assert(wrk->y_accum <= 0);
for (x_out = 0; x_out < wrk->dst_width; ++x_out) {
const int frac = (int)MULT(wrk->frow[x_out], yscale);
const int v = (int)MULT(wrk->irow[x_out] - frac, wrk->fxy_scale);
for (x_out = 0; x_out < x_out_max; ++x_out) {
const int frac = (int)MULT_FIX(wrk->frow[x_out], yscale);
const int v = (int)MULT_FIX(wrk->irow[x_out] - frac, wrk->fxy_scale);
wrk->dst[x_out] = (!(v & ~0xff)) ? v : (v < 0) ? 0 : 255;
wrk->irow[x_out] = frac; // new fractional start
}
@ -744,7 +752,7 @@ void WebPRescalerExportRow(WebPRescaler* const wrk) {
wrk->dst += wrk->dst_stride;
}
#undef MULT
#undef MULT_FIX
#undef RFIX
//------------------------------------------------------------------------------