Specify a channel as having premultiplied alpha and use it to un-premultiply all other channels before resampling.
This commit is contained in:
Jorge Rodriguez
parent
a32fa8b4df
commit
8063ea0952
@ -51,12 +51,13 @@
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// result = stbr_resize_arbitrary(input_data, input_w, input_h, input_stride_in_bytes,
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// output_data, output_w, output_h, output_stride_in_bytes,
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// s0, t0, s1, t1,
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// channels, STBR_TYPE_UINT8, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB,
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// channels, premultiplied_alpha_channel, STBR_TYPE_UINT8, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB,
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// extra_memory, memory_required);
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// free(extra_memory);
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//
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// input_stride_in_bytes and output_stride_in_bytes can be 0. If so they will be automatically calculated as width * channels.
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// s0, t0, s1, t1 are the top-left and bottom right corner (uv addressing style: [0, 1]x[0, 1]) of a region of the input image to use.
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// premultiplied_alpha_channel is 0 if there are no premultiplied alpha channels. If nonzero, the specified channel will be divided from all other channels before resampling, then multiplied back in after.
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// Returned result is 1 for success or 0 in case of an error. In the case of an error an assert with be triggered, #define STBR_ASSERT() to see it.
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// stbr_resize_arbitrary() will not allocate any memory, it will use the memory you pass in to do its work.
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@ -155,7 +156,7 @@ extern "C" {
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STBRDEF int stbr_resize_arbitrary(const void* input_data, int input_w, int input_h, int input_stride_in_bytes,
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void* output_data, int output_w, int output_h, int output_stride_in_bytes,
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float s0, float t0, float s1, float t1,
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int channels, stbr_type type, stbr_filter filter, stbr_edge edge, stbr_colorspace colorspace,
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int channels, int premultiplied_alpha_channel, stbr_type type, stbr_filter filter, stbr_edge edge, stbr_colorspace colorspace,
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void* tempmem, stbr_size_t tempmem_size_in_bytes);
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@ -256,6 +257,7 @@ typedef struct
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float vertical_scale;
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int channels;
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int premul_alpha_channel;
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stbr_type type;
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stbr_filter filter;
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stbr_edge edge;
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@ -708,6 +710,7 @@ static void stbr__decode_scanline(stbr__info* stbr_info, int n)
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{
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int x, c;
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int channels = stbr_info->channels;
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int premul_alpha_channel = stbr_info->premul_alpha_channel;
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int type = stbr_info->type;
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int colorspace = stbr_info->colorspace;
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int input_w = stbr_info->input_w;
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@ -770,6 +773,17 @@ static void stbr__decode_scanline(stbr__info* stbr_info, int n)
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STBR_UNIMPLEMENTED("Unknown type/colorspace/channels combination.");
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break;
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}
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if (premul_alpha_channel)
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{
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for (c = 0; c < channels; c++)
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{
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if (c == premul_alpha_channel)
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continue;
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decode_buffer[decode_texel_index + c] /= decode_buffer[decode_texel_index + premul_alpha_channel];
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}
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}
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}
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}
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@ -920,9 +934,21 @@ static float* stbr__get_ring_buffer_scanline(int get_scanline, float* ring_buffe
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}
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static stbr_inline void stbr__encode_scanline(void* output_buffer, int output_texel_index, float* encode_buffer, int encode_texel_index, int channels, int decode)
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static stbr_inline void stbr__encode_scanline(void* output_buffer, int output_texel_index, float* encode_buffer, int encode_texel_index, int channels, int premul_alpha_channel, int decode)
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{
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int n;
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if (premul_alpha_channel)
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{
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for (n = 0; n < channels; n++)
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{
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if (n == premul_alpha_channel)
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continue;
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encode_buffer[encode_texel_index + n] *= encode_buffer[encode_texel_index + premul_alpha_channel];
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}
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}
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switch (decode)
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{
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case STBR__DECODE(STBR_TYPE_UINT8, STBR_COLORSPACE_LINEAR):
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@ -969,6 +995,18 @@ static stbr_inline void stbr__encode_scanline(void* output_buffer, int output_te
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STBR_UNIMPLEMENTED("Unknown type/colorspace/channels combination.");
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break;
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}
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// Put it back the way it was in case this is a ring buffer.
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if (premul_alpha_channel)
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{
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for (n = 0; n < channels; n++)
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{
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if (n == premul_alpha_channel)
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continue;
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encode_buffer[encode_texel_index + n] /= encode_buffer[encode_texel_index + premul_alpha_channel];
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}
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}
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}
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static void stbr__resample_vertical_upsample(stbr__info* stbr_info, int n, int in_first_scanline, int in_last_scanline, float in_center_of_out)
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@ -978,6 +1016,7 @@ static void stbr__resample_vertical_upsample(stbr__info* stbr_info, int n, int i
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stbr__contributors* vertical_contributors = &stbr_info->vertical_contributors;
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float* vertical_coefficients = stbr_info->vertical_coefficients;
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int channels = stbr_info->channels;
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int premul_alpha_channel = stbr_info->premul_alpha_channel;
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int type = stbr_info->type;
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int colorspace = stbr_info->colorspace;
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int kernel_texel_width = stbr__get_filter_texel_width_vertical(stbr_info);
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@ -1023,7 +1062,7 @@ static void stbr__resample_vertical_upsample(stbr__info* stbr_info, int n, int i
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encode_buffer[c] += ring_buffer_entry[in_texel_index + c] * coefficient;
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}
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stbr__encode_scanline(output_data, out_texel_index, encode_buffer, 0, channels, decode);
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stbr__encode_scanline(output_data, out_texel_index, encode_buffer, 0, channels, premul_alpha_channel, decode);
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}
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}
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@ -1130,6 +1169,7 @@ static void stbr__empty_ring_buffer(stbr__info* stbr_info, int first_necessary_s
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{
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int output_stride = stbr_info->output_stride_bytes / stbr__type_size[stbr_info->type];
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int channels = stbr_info->channels;
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int premul_alpha_channel = stbr_info->premul_alpha_channel;
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int type = stbr_info->type;
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int colorspace = stbr_info->colorspace;
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int output_w = stbr_info->output_w;
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@ -1156,7 +1196,7 @@ static void stbr__empty_ring_buffer(stbr__info* stbr_info, int first_necessary_s
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int ring_texel_index = texel_index;
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int output_texel_index = output_row + texel_index;
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stbr__encode_scanline(output_data, output_texel_index, ring_buffer_entry, ring_texel_index, channels, decode);
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stbr__encode_scanline(output_data, output_texel_index, ring_buffer_entry, ring_texel_index, channels, premul_alpha_channel, decode);
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}
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}
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@ -1221,7 +1261,7 @@ static void stbr__buffer_loop_downsample(stbr__info* stbr_info)
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STBRDEF int stbr_resize_arbitrary(const void* input_data, int input_w, int input_h, int input_stride_in_bytes,
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void* output_data, int output_w, int output_h, int output_stride_in_bytes,
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float s0, float t0, float s1, float t1,
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int channels, stbr_type type, stbr_filter filter, stbr_edge edge, stbr_colorspace colorspace,
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int channels, int premul_alpha_channel, stbr_type type, stbr_filter filter, stbr_edge edge, stbr_colorspace colorspace,
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void* tempmem, stbr_size_t tempmem_size_in_bytes)
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{
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stbr_size_t memory_required = stbr_calculate_memory(input_w, input_h, output_w, output_h, s0, t0, s1, t1, channels, filter);
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@ -1260,6 +1300,11 @@ STBRDEF int stbr_resize_arbitrary(const void* input_data, int input_w, int input
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if (s1 > 1 || s0 < 0 || t1 > 1 || t0 < 0)
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return 0;
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STBR_ASSERT(premul_alpha_channel >= 0 && premul_alpha_channel < channels);
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if (premul_alpha_channel < 0 || premul_alpha_channel >= channels)
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return 0;
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STBR_ASSERT(tempmem);
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if (!tempmem)
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@ -1296,6 +1341,7 @@ STBRDEF int stbr_resize_arbitrary(const void* input_data, int input_w, int input
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stbr_info->vertical_shift = t0 * input_h / (t1 - t0);
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stbr_info->channels = channels;
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stbr_info->premul_alpha_channel = premul_alpha_channel;
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stbr_info->type = type;
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stbr_info->filter = filter;
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stbr_info->edge = edge;
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@ -1396,7 +1442,7 @@ STBRDEF int stbr_resize_srgb_uint8(const stbr_uint8* input_data, int input_w, in
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if (!extra_memory)
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return 0;
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int result = stbr_resize_arbitrary(input_data, input_w, input_h, 0, output_data, output_w, output_h, 0, 0, 0, 1, 1, channels, STBR_TYPE_UINT8, filter, edge, STBR_COLORSPACE_SRGB, extra_memory, memory_required);
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int result = stbr_resize_arbitrary(input_data, input_w, input_h, 0, output_data, output_w, output_h, 0, 0, 0, 1, 1, channels, 0, STBR_TYPE_UINT8, filter, edge, STBR_COLORSPACE_SRGB, extra_memory, memory_required);
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free(extra_memory);
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@ -1413,7 +1459,7 @@ STBRDEF int stbr_resize_srgb_uint16(const stbr_uint16* input_data, int input_w,
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if (!extra_memory)
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return 0;
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int result = stbr_resize_arbitrary(input_data, input_w, input_h, 0, output_data, output_w, output_h, 0, 0, 0, 1, 1, channels, STBR_TYPE_UINT16, filter, edge, STBR_COLORSPACE_SRGB, extra_memory, memory_required);
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int result = stbr_resize_arbitrary(input_data, input_w, input_h, 0, output_data, output_w, output_h, 0, 0, 0, 1, 1, channels, 0, STBR_TYPE_UINT16, filter, edge, STBR_COLORSPACE_SRGB, extra_memory, memory_required);
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free(extra_memory);
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@ -1430,7 +1476,7 @@ STBRDEF int stbr_resize_srgb_uint32(const stbr_uint32* input_data, int input_w,
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if (!extra_memory)
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return 0;
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int result = stbr_resize_arbitrary(input_data, input_w, input_h, 0, output_data, output_w, output_h, 0, 0, 0, 1, 1, channels, STBR_TYPE_UINT32, filter, edge, STBR_COLORSPACE_SRGB, extra_memory, memory_required);
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int result = stbr_resize_arbitrary(input_data, input_w, input_h, 0, output_data, output_w, output_h, 0, 0, 0, 1, 1, channels, 0, STBR_TYPE_UINT32, filter, edge, STBR_COLORSPACE_SRGB, extra_memory, memory_required);
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free(extra_memory);
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@ -1447,7 +1493,7 @@ STBRDEF int stbr_resize_srgb_float(const float* input_data, int input_w, int inp
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if (!extra_memory)
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return 0;
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int result = stbr_resize_arbitrary(input_data, input_w, input_h, 0, output_data, output_w, output_h, 0, 0, 0, 1, 1, channels, STBR_TYPE_FLOAT, filter, edge, STBR_COLORSPACE_SRGB, extra_memory, memory_required);
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int result = stbr_resize_arbitrary(input_data, input_w, input_h, 0, output_data, output_w, output_h, 0, 0, 0, 1, 1, channels, 0, STBR_TYPE_FLOAT, filter, edge, STBR_COLORSPACE_SRGB, extra_memory, memory_required);
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free(extra_memory);
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@ -91,7 +91,7 @@ int main(int argc, char** argv)
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printf("Average: %dms\n", average);
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#else
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stbr_resize_arbitrary(input_data + w * border * n + border * n, in_w, in_h, w*n, output_data, out_w, out_h, out_stride, s0, t0, s1, t1, n, STBR_TYPE_UINT8, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB, extra_memory, memory_required);
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stbr_resize_arbitrary(input_data + w * border * n + border * n, in_w, in_h, w*n, output_data, out_w, out_h, out_stride, s0, t0, s1, t1, n, 0, STBR_TYPE_UINT8, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB, extra_memory, memory_required);
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#endif
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free(extra_memory);
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@ -123,7 +123,7 @@ void resize_image(const char* filename, float width_percent, float height_percen
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size_t memory_required = stbr_calculate_memory(w, h, out_w, out_h, 0, 0, 1, 1, n, filter);
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void* extra_memory = malloc(memory_required);
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stbr_resize_arbitrary(input_data, w, h, 0, output_data, out_w, out_h, 0, 0, 0, 1, 1, n, STBR_TYPE_UINT8, filter, edge, colorspace, extra_memory, memory_required);
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stbr_resize_arbitrary(input_data, w, h, 0, output_data, out_w, out_h, 0, 0, 0, 1, 1, n, 0, STBR_TYPE_UINT8, filter, edge, colorspace, extra_memory, memory_required);
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free(extra_memory);
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stbi_image_free(input_data);
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@ -157,7 +157,7 @@ void test_format(const char* file, float width_percent, float height_percent, st
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size_t required = stbr_calculate_memory(w, h, new_w, new_h, 0, 0, 1, 1, n, STBR_FILTER_CATMULLROM);
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void* extra_memory = malloc(required);
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stbr_resize_arbitrary(T_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, 1, 1, n, type, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, colorspace, extra_memory, required);
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stbr_resize_arbitrary(T_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, 1, 1, n, 0, type, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, colorspace, extra_memory, required);
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free(extra_memory);
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free(T_data);
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@ -201,7 +201,7 @@ void test_float(const char* file, float width_percent, float height_percent, stb
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size_t required = stbr_calculate_memory(w, h, new_w, new_h, 0, 0, 1, 1, n, STBR_FILTER_CATMULLROM);
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void* extra_memory = malloc(required);
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stbr_resize_arbitrary(T_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, 1, 1, n, type, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, colorspace, extra_memory, required);
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stbr_resize_arbitrary(T_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, 1, 1, n, 0, type, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, colorspace, extra_memory, required);
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free(extra_memory);
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free(T_data);
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@ -267,7 +267,7 @@ void test_subpixel(const char* file, float width_percent, float height_percent,
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size_t tempmem_size = stbr_calculate_memory(w, h, new_w, new_h, 0, 0, s1, t1, n, STBR_FILTER_CATMULLROM);
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void* tempmem = malloc(tempmem_size);
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stbr_resize_arbitrary(input_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, s1, t1, n, STBR_TYPE_UINT8, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB, tempmem, tempmem_size);
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stbr_resize_arbitrary(input_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, s1, t1, n, 0, STBR_TYPE_UINT8, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB, tempmem, tempmem_size);
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free(tempmem);
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@ -280,8 +280,43 @@ void test_subpixel(const char* file, float width_percent, float height_percent,
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free(output_data);
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}
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void test_premul(const char* file)
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{
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int w, h, n;
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unsigned char* input_data = stbi_load(file, &w, &h, &n, 4);
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n = 4;
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// Premultiply the first texel.
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input_data[0] /= 2;
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input_data[1] /= 2;
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input_data[2] /= 2;
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input_data[3] = 255 / 2;
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int new_w = (int)(w * .5);
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int new_h = (int)(h * .5);
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unsigned char* output_data = (unsigned char*)malloc(new_w * new_h * n * sizeof(unsigned char));
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size_t tempmem_size = stbr_calculate_memory(w, h, new_w, new_h, 0, 0, 1, 1, n, STBR_FILTER_CATMULLROM);
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void* tempmem = malloc(tempmem_size);
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stbr_resize_arbitrary(input_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, 1, 1, n, 3, STBR_TYPE_UINT8, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB, tempmem, tempmem_size);
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free(tempmem);
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stbi_image_free(input_data);
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char output[200];
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sprintf(output, "test-output/premul-%s", file);
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stbi_write_png(output, new_w, new_h, n, output_data, 0);
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free(output_data);
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}
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void test_suite()
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{
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test_premul("barbara.png");
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for (int i = 0; i < 10; i++)
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test_subpixel("barbara.png", 0.5f, 0.5f, (float)i / 10, 1);
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