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PNM decoding: handle max_value != 255

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also add support for PAM's GRAYSCALE_ALPHA tuple (with depth = 2)

BUG=webp:449

Change-Id: I0fe4825cd1d5487b9f7af332c7d3d56c1b35c3fb
This commit is contained in:
Pascal Massimino 2020-01-04 16:08:45 +01:00 committed by Skal
parent cf047e8347
commit 6cf504d018
1 changed files with 59 additions and 21 deletions
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80
imageio/pnmdec.c
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@ -33,8 +33,8 @@ typedef struct {
const uint8_t* data;
size_t data_size;
int width, height;
int bytes_per_px; // 1, 3, 4
int depth;
int bytes_per_px;
int depth; // 1 (grayscale), 2 (grayscale + alpha), 3 (rgb), 4 (rgba)
int max_value;
int type; // 5, 6 or 7
int seen_flags;
@ -101,6 +101,9 @@ static size_t ReadPAMFields(PNMInfo* const info, size_t off) {
} else if (!strcmp(out, "TUPLTYPE RGB")) {
expected_depth = 3;
info->seen_flags |= TUPLE_FLAG;
} else if (!strcmp(out, "TUPLTYPE GRAYSCALE_ALPHA")) {
expected_depth = 2;
info->seen_flags |= TUPLE_FLAG;
} else if (!strcmp(out, "TUPLTYPE GRAYSCALE")) {
expected_depth = 1;
info->seen_flags |= TUPLE_FLAG;
@ -166,7 +169,7 @@ static size_t ReadHeader(PNMInfo* const info) {
// perform some basic numerical validation
if (info->width <= 0 || info->height <= 0 ||
info->type <= 0 || info->type >= 9 ||
info->depth <= 0 || info->depth == 2 || info->depth > 4 ||
info->depth <= 0 || info->depth > 4 ||
info->max_value <= 0 || info->max_value >= 65536) {
return 0;
}
@ -179,7 +182,7 @@ int ReadPNM(const uint8_t* const data, size_t data_size,
struct Metadata* const metadata) {
int ok = 0;
int i, j;
uint64_t stride, pixel_bytes;
uint64_t stride, pixel_bytes, sample_size, depth;
uint8_t* rgb = NULL, *tmp_rgb;
size_t offset;
PNMInfo info;
@ -210,8 +213,10 @@ int ReadPNM(const uint8_t* const data, size_t data_size,
fprintf(stderr, "Truncated PNM file (P%d).\n", info.type);
goto End;
}
stride =
(uint64_t)(info.bytes_per_px < 3 ? 3 : info.bytes_per_px) * info.width;
sample_size = (info.max_value > 255) ? 2 : 1;
// final depth
depth = (info.depth == 1 || info.depth == 3 || !keep_alpha) ? 3 : 4;
stride = depth * info.width;
if (stride != (size_t)stride ||
!ImgIoUtilCheckSizeArgumentsOverflow(stride, info.height)) {
goto End;
@ -220,30 +225,63 @@ int ReadPNM(const uint8_t* const data, size_t data_size,
rgb = (uint8_t*)malloc((size_t)stride * info.height);
if (rgb == NULL) goto End;
// Convert input
// Convert input.
// We only optimize for the sample_size=1, max_value=255, depth=1 case.
tmp_rgb = rgb;
for (j = 0; j < info.height; ++j) {
assert(offset + info.bytes_per_px * info.width <= data_size);
if (info.depth == 1) {
// convert grayscale -> RGB
for (i = 0; i < info.width; ++i) {
const uint8_t v = data[offset + i];
tmp_rgb[3 * i + 0] = tmp_rgb[3 * i + 1] = tmp_rgb[3 * i + 2] = v;
}
} else if (info.depth == 3) { // RGB
memcpy(tmp_rgb, data + offset, 3 * info.width * sizeof(*data));
} else if (info.depth == 4) { // RGBA
memcpy(tmp_rgb, data + offset, 4 * info.width * sizeof(*data));
}
const uint8_t* in = data + offset;
offset += info.bytes_per_px * info.width;
assert(offset <= data_size);
if (info.max_value == 255 && info.depth >= 3) {
// RGB or RGBA
if (info.depth == 3 || keep_alpha) {
memcpy(tmp_rgb, in, info.depth * info.width * sizeof(*in));
} else {
assert(info.depth == 4 && !keep_alpha);
for (i = 0; i < info.width; ++i) {
tmp_rgb[3 * i + 0] = in[4 * i + 0];
tmp_rgb[3 * i + 1] = in[4 * i + 1];
tmp_rgb[3 * i + 2] = in[4 * i + 2];
}
}
} else {
// Unoptimized case, we need to handle non-trivial operations:
// * convert 16b to 8b (if max_value > 255)
// * rescale to [0..255] range (if max_value != 255)
// * drop the alpha channel (if keep_alpha is false)
const uint32_t round = info.max_value / 2;
int k = 0;
for (i = 0; i < info.width * info.depth; ++i) {
uint32_t v = (sample_size == 2) ? 256u * in[2 * i + 0] + in[2 * i + 1]
: in[i];
if (info.max_value != 255) v = (v * 255u + round) / info.max_value;
if (v > 255u) v = 255u;
if (info.depth > 2) {
if (!keep_alpha && info.depth == 4 && (i % 4) == 3) {
// skip alpha
} else {
tmp_rgb[k] = v;
k += 1;
}
} else if (info.depth == 1 || (i % 2) == 0) {
tmp_rgb[k + 0] = tmp_rgb[k + 1] = tmp_rgb[k + 2] = v;
k += 3;
} else if (keep_alpha && info.depth == 2) {
tmp_rgb[k] = v;
k += 1;
} else {
// skip alpha
}
}
}
tmp_rgb += stride;
}
// WebP conversion.
pic->width = info.width;
pic->height = info.height;
ok = (info.depth == 4) ? WebPPictureImportRGBA(pic, rgb, (int)stride)
: WebPPictureImportRGB(pic, rgb, (int)stride);
ok = (depth == 4) ? WebPPictureImportRGBA(pic, rgb, (int)stride)
: WebPPictureImportRGB(pic, rgb, (int)stride);
if (!ok) goto End;
ok = 1;