static int EncodeAlphaInternal(const uint8_t* const data, int width, int height,
int method, int filter, int reduce_levels,
int effort_level, // in [0..6] range
uint8_t* const tmp_alpha,
VP8BitWriter* const bw,
WebPAuxStats* const stats) {
int ok = 0;
const uint8_t* alpha_src;
WebPFilterFunc filter_func;
uint8_t header;
size_t expected_size;
const size_t data_size = width * height;
assert((uint64_t)data_size == (uint64_t)width * height); // as per spec
assert(filter >= 0 && filter < WEBP_FILTER_LAST);
assert(method >= ALPHA_NO_COMPRESSION);
assert(method <= ALPHA_LOSSLESS_COMPRESSION);
assert(sizeof(header) == ALPHA_HEADER_LEN);
// TODO(skal): have a common function and #define's to validate alpha params.
expected_size =
(method == ALPHA_NO_COMPRESSION) ? (ALPHA_HEADER_LEN + data_size)
: (data_size >> 5);
header = method | (filter << 2);
if (reduce_levels) header |= ALPHA_PREPROCESSED_LEVELS << 4;
VP8BitWriterInit(bw, expected_size);
VP8BitWriterAppend(bw, &header, ALPHA_HEADER_LEN);
filter_func = WebPFilters[filter];
if (filter_func) {
filter_func(data, width, height, 1, width, tmp_alpha);
alpha_src = tmp_alpha;
} else {
alpha_src = data;
}
if (method == ALPHA_NO_COMPRESSION) {
ok = VP8BitWriterAppend(bw, alpha_src, width * height);
ok = ok && !bw->error_;
} else {
ok = EncodeLossless(alpha_src, width, height, effort_level, bw, stats);
VP8BitWriterFinish(bw);
}
return ok;
}
// This function always returns an initialized 'bw' object, even upon error.
static int EncodeAlphaInternal(const uint8_t* const data, int width, int height,
int method, int filter, int reduce_levels,
int effort_level, // in [0..6] range
uint8_t* const tmp_alpha,
FilterTrial* result) {
int ok = 0;
const uint8_t* alpha_src;
WebPFilterFunc filter_func;
uint8_t header;
const size_t data_size = width * height;
const uint8_t* output = NULL;
size_t output_size = 0;
VP8LBitWriter tmp_bw;
assert((uint64_t)data_size == (uint64_t)width * height); // as per spec
assert(filter >= 0 && filter < WEBP_FILTER_LAST);
assert(method >= ALPHA_NO_COMPRESSION);
assert(method <= ALPHA_LOSSLESS_COMPRESSION);
assert(sizeof(header) == ALPHA_HEADER_LEN);
// TODO(skal): have a common function and #define's to validate alpha params.
filter_func = WebPFilters[filter];
if (filter_func != NULL) {
filter_func(data, width, height, width, tmp_alpha);
alpha_src = tmp_alpha;
} else {
alpha_src = data;
}
if (method != ALPHA_NO_COMPRESSION) {
ok = VP8LBitWriterInit(&tmp_bw, data_size >> 3);
ok = ok && EncodeLossless(alpha_src, width, height, effort_level,
&tmp_bw, &result->stats);
if (ok) {
output = VP8LBitWriterFinish(&tmp_bw);
output_size = VP8LBitWriterNumBytes(&tmp_bw);
if (output_size > data_size) {
// compressed size is larger than source! Revert to uncompressed mode.
method = ALPHA_NO_COMPRESSION;
VP8LBitWriterDestroy(&tmp_bw);
}
} else {
VP8LBitWriterDestroy(&tmp_bw);
return 0;
}
}
