+wxImage wxImage::ResampleBox(int width, int height) const
+{
+ // This function implements a simple pre-blur/box averaging method for downsampling that gives reasonably smooth results
+ // To scale the image down we will need to gather a grid of pixels of the size of the scale factor in each direction
+ // and then do an averaging of the pixels.
+
+ wxImage ret_image(width, height, false);
+
+ double scale_factor_x = double(M_IMGDATA->m_width) / width;
+ double scale_factor_y = double(M_IMGDATA->m_height) / height;
+
+ // If we want good-looking results we need to pre-blur the image a bit first
+ wxImage src_image(*this);
+ src_image = src_image.BlurHorizontal(scale_factor_x / 2);
+ src_image = src_image.BlurVertical(scale_factor_y / 2);
+
+ unsigned char* src_data = src_image.GetData();
+ unsigned char* src_alpha = src_image.GetAlpha();
+ unsigned char* dst_data = ret_image.GetData();
+ unsigned char* dst_alpha = NULL;
+
+ if(src_alpha)
+ {
+ ret_image.SetAlpha();
+ dst_alpha = ret_image.GetAlpha();
+ }
+
+ int x, y, i, j;
+ int averaged_pixels, src_pixel_index, src_x, src_y;
+ double sum_r, sum_g, sum_b, sum_a;
+
+ for(y = 0; y < height; y++) // Destination image - Y direction
+ {
+ // Source pixel in the Y direction
+ src_y = y * scale_factor_y;
+
+ for(x = 0; x < width; x++) // Destination image - X direction
+ {
+ // Source pixel in the X direction
+ src_x = x * scale_factor_x;
+
+ // Box of pixels to average
+ averaged_pixels = 0;
+ sum_r = sum_g = sum_b = sum_a = 0.0;
+
+ for(j = src_y - scale_factor_y / 2 + 1; j <= int(src_y + scale_factor_y / 2); j++) // Y direction
+ {
+ // We don't care to average pixels that don't exist (edges)
+ if(j < 0 || j > M_IMGDATA->m_height)
+ continue;
+
+ for(i = src_x - scale_factor_x / 2 + 1; i <= int(src_x + scale_factor_x / 2); i++) // X direction
+ {
+ // Don't average edge pixels
+ if(i < 0 || i > M_IMGDATA->m_width)
+ continue;
+
+ // Calculate the actual index in our source pixels
+ src_pixel_index = src_y * M_IMGDATA->m_width + src_x;
+
+ sum_r += src_data[src_pixel_index * 3 + 0];
+ sum_g += src_data[src_pixel_index * 3 + 1];
+ sum_b += src_data[src_pixel_index * 3 + 2];
+ if(src_alpha)
+ sum_a += src_alpha[src_pixel_index];
+
+ averaged_pixels++;
+ }
+ }
+
+ // Calculate the average from the sum and number of averaged pixels
+ dst_data[0] = int(sum_r / averaged_pixels);
+ dst_data[1] = int(sum_g / averaged_pixels);
+ dst_data[2] = int(sum_b / averaged_pixels);
+ dst_data += 3;
+ if(src_alpha)
+ *dst_alpha++ = sum_a / averaged_pixels;
+ }
+ }
+
+ return ret_image;
+}
+
+// The following two local functions are for the B-spline weighting of the bicubic sampling algorithm
+static inline double spline_cube(double value)
+{
+ return value <= 0.0 ? 0.0 : value * value * value;
+}
+
+static inline double spline_weight(double value)
+{
+ return (spline_cube(value + 2) - 4 * spline_cube(value + 1) + 6 * spline_cube(value) - 4 * spline_cube(value - 1)) / 6;
+}
+
+// This is the bicubic resampling algorithm
+wxImage wxImage::ResampleBicubic(int width, int height) const
+{
+ // This function implements a Bicubic B-Spline algorithm for resampling. This method is certainly a little slower than wxImage's default
+ // pixel replication method, however for most reasonably sized images not being upsampled too much on a fairly average CPU this
+ // difference is hardly noticeable and the results are far more pleasing to look at.
+ //
+ // This particular bicubic algorithm does pixel weighting according to a B-Spline that basically implements a Gaussian bell-like
+ // weighting kernel. Because of this method the results may appear a bit blurry when upsampling by large factors. This is basically
+ // because a slight gaussian blur is being performed to get the smooth look of the upsampled image.
+
+ // Edge pixels: 3-4 possible solutions
+ // - (Wrap/tile) Wrap the image, take the color value from the opposite side of the image.
+ // - (Mirror) Duplicate edge pixels, so that pixel at coordinate (2, n), where n is nonpositive, will have the value of (2, 1).
+ // - (Ignore) Simply ignore the edge pixels and apply the kernel only to pixels which do have all neighbours.
+ // - (Clamp) Choose the nearest pixel along the border. This takes the border pixels and extends them out to infinity.
+ //
+ // NOTE: below the y_offset and x_offset variables are being set for edge pixels using the "Mirror" method mentioned above
+
+ wxImage ret_image;
+
+ ret_image.Create(width, height, false);
+
+ unsigned char* src_data = M_IMGDATA->m_data;
+ unsigned char* src_alpha = M_IMGDATA->m_alpha;
+ unsigned char* dst_data = ret_image.GetData();
+ unsigned char* dst_alpha = NULL;
+
+ if(src_alpha)
+ {
+ ret_image.SetAlpha();
+ dst_alpha = ret_image.GetAlpha();
+ }
+
+ int k, i;
+ double srcpixx, srcpixy, dx, dy;
+ int dstx, dsty;
+ double sum_r = 0, sum_g = 0, sum_b = 0, sum_a = 0; // Sums for each color channel
+ int x_offset = 0, y_offset = 0;
+ double pixel_weight;
+ long src_pixel_index;
+
+ for(dsty = 0; dsty < height; dsty++)
+ {
+ // We need to calculate the source pixel to interpolate from - Y-axis
+ srcpixy = double(dsty) * M_IMGDATA->m_height / height;
+ dy = srcpixy - (int)srcpixy;
+
+ for(dstx = 0; dstx < width; dstx++)
+ {
+ // X-axis of pixel to interpolate from
+ srcpixx = double(dstx) * M_IMGDATA->m_width / width;
+ dx = srcpixx - (int)srcpixx;
+
+ // Clear all the RGBA sum values
+ sum_r = sum_g = sum_b = sum_a = 0;
+
+ // Here we actually determine the RGBA values for the destination pixel
+ for(k = -1; k <= 2; k++)
+ {
+ // Y offset
+ y_offset = srcpixy + double(k) < 0.0 ? 0 : (srcpixy + double(k) >= M_IMGDATA->m_height ? M_IMGDATA->m_height - 1 : srcpixy + k);
+
+ // Loop across the X axis
+ for(i = -1; i <= 2; i++)
+ {
+ // X offset
+ x_offset = srcpixx + double(i) < 0.0 ? 0 : (srcpixx + double(i) >= M_IMGDATA->m_width ? M_IMGDATA->m_width - 1 : srcpixx + i);
+
+ // Calculate the exact position where the source data should be pulled from based on the x_offset and y_offset
+ src_pixel_index = (y_offset * M_IMGDATA->m_width) + x_offset;
+
+ // Calculate the weight for the specified pixel according to the bicubic b-spline kernel we're using for interpolation
+ pixel_weight = spline_weight(double(i) - dx) * spline_weight(double(k) - dy);
+
+ // Create a sum of all velues for each color channel adjusted for the pixel's calculated weight
+ sum_r += double(src_data[src_pixel_index * 3 + 0]) * pixel_weight;
+ sum_g += double(src_data[src_pixel_index * 3 + 1]) * pixel_weight;
+ sum_b += double(src_data[src_pixel_index * 3 + 2]) * pixel_weight;
+ if(src_alpha)
+ sum_a += double(src_alpha[src_pixel_index]) * pixel_weight;
+ }
+ }
+
+ // Put the data into the destination image. The summed values are of double data type and are rounded here for accuracy
+ dst_data[0] = int(sum_r + 0.5);
+ dst_data[1] = int(sum_g + 0.5);
+ dst_data[2] = int(sum_b + 0.5);
+ dst_data += 3;
+
+ if(src_alpha)
+ *dst_alpha++ = sum_a;
+ }
+ }
+
+ return ret_image;
+}
+
+// Blur in the horizontal direction
+wxImage wxImage::BlurHorizontal(int blurRadius)
+{
+ wxImage ret_image;
+ ret_image.Create(M_IMGDATA->m_width, M_IMGDATA->m_height, false);
+
+ unsigned char* src_data = M_IMGDATA->m_data;
+ unsigned char* dst_data = ret_image.GetData();
+ unsigned char* src_alpha = M_IMGDATA->m_alpha;
+ unsigned char* dst_alpha = NULL;
+
+ // Check for a mask or alpha
+ if(M_IMGDATA->m_hasMask)
+ ret_image.SetMaskColour(M_IMGDATA->m_maskRed, M_IMGDATA->m_maskGreen, M_IMGDATA->m_maskBlue);
+ else
+ if(src_alpha)
+ {
+ ret_image.SetAlpha();
+ dst_alpha = ret_image.GetAlpha();
+ }
+
+ // Variables used in the blurring algorithm
+ int x, y;
+ int kernel_x;
+ long sum_r, sum_g, sum_b, sum_a;
+ long pixel_idx;
+
+ // Horizontal blurring algorithm - average all pixels in the specified blur radius in the X or horizontal direction
+ for(y = 0; y < M_IMGDATA->m_height; y++)
+ {
+ sum_r = sum_g = sum_b = sum_a = 0;
+
+ // Calculate the average of all pixels in the blur radius for the first pixel of the row
+ for(kernel_x = -blurRadius; kernel_x <= blurRadius; kernel_x++)
+ {
+ // To deal with the pixels at the start of a row so it's not grabbing GOK values from memory at negative indices of the image's data or grabbing from the previous row
+ if(kernel_x < 0)
+ pixel_idx = y * M_IMGDATA->m_width;
+ else
+ pixel_idx = kernel_x + y * M_IMGDATA->m_width;
+
+ sum_r += src_data[pixel_idx * 3 + 0];
+ sum_g += src_data[pixel_idx * 3 + 1];
+ sum_b += src_data[pixel_idx * 3 + 2];
+ sum_a += src_alpha ? src_alpha[pixel_idx] : 0;
+ }
+ dst_data[y * M_IMGDATA->m_width * 3 + 0] = sum_r / (blurRadius * 2 + 1);
+ dst_data[y * M_IMGDATA->m_width * 3 + 1] = sum_g / (blurRadius * 2 + 1);
+ dst_data[y * M_IMGDATA->m_width * 3 + 2] = sum_b / (blurRadius * 2 + 1);
+ if(src_alpha)
+ dst_alpha[y * M_IMGDATA->m_width] = sum_a / (blurRadius * 2 + 1);
+
+ // Now average the values of the rest of the pixels by just moving the blur radius box along the row
+ for(x = 1; x < M_IMGDATA->m_width; x++)
+ {
+ // Take care of edge pixels on the left edge by essentially duplicating the edge pixel
+ if(x - blurRadius - 1 < 0)
+ pixel_idx = y * M_IMGDATA->m_width;
+ else
+ pixel_idx = (x - blurRadius - 1) + y * M_IMGDATA->m_width;
+
+ // Subtract the value of the pixel at the left side of the blur radius box
+ sum_r -= src_data[pixel_idx * 3 + 0];
+ sum_g -= src_data[pixel_idx * 3 + 1];
+ sum_b -= src_data[pixel_idx * 3 + 2];
+ sum_a -= src_alpha ? src_alpha[pixel_idx] : 0;
+
+ // Take care of edge pixels on the right edge
+ if(x + blurRadius > M_IMGDATA->m_width - 1)
+ pixel_idx = M_IMGDATA->m_width - 1 + y * M_IMGDATA->m_width;
+ else
+ pixel_idx = x + blurRadius + y * M_IMGDATA->m_width;
+
+ // Add the value of the pixel being added to the end of our box
+ sum_r += src_data[pixel_idx * 3 + 0];
+ sum_g += src_data[pixel_idx * 3 + 1];
+ sum_b += src_data[pixel_idx * 3 + 2];
+ sum_a += src_alpha ? src_alpha[pixel_idx] : 0;
+
+ // Save off the averaged data
+ dst_data[x * 3 + y * M_IMGDATA->m_width * 3 + 0] = sum_r / (blurRadius * 2 + 1);
+ dst_data[x * 3 + y * M_IMGDATA->m_width * 3 + 1] = sum_g / (blurRadius * 2 + 1);
+ dst_data[x * 3 + y * M_IMGDATA->m_width * 3 + 2] = sum_b / (blurRadius * 2 + 1);
+ if(src_alpha)
+ dst_alpha[x + y * M_IMGDATA->m_width] = sum_a / (blurRadius * 2 + 1);
+ }
+ }
+
+ return ret_image;
+}
+
+// Blur in the vertical direction
+wxImage wxImage::BlurVertical(int blurRadius)
+{
+ wxImage ret_image;
+ ret_image.Create(M_IMGDATA->m_width, M_IMGDATA->m_height, false);
+
+ unsigned char* src_data = M_IMGDATA->m_data;
+ unsigned char* dst_data = ret_image.GetData();
+ unsigned char* src_alpha = M_IMGDATA->m_alpha;
+ unsigned char* dst_alpha = NULL;
+
+ // Check for a mask or alpha
+ if(M_IMGDATA->m_hasMask)
+ ret_image.SetMaskColour(M_IMGDATA->m_maskRed, M_IMGDATA->m_maskGreen, M_IMGDATA->m_maskBlue);
+ else
+ if(src_alpha)
+ {
+ ret_image.SetAlpha();
+ dst_alpha = ret_image.GetAlpha();
+ }
+
+ // Variables used in the blurring algorithm
+ int x, y;
+ int kernel_y;
+ long sum_r, sum_g, sum_b, sum_a;
+ long pixel_idx;
+
+ // Vertical blurring algorithm - same as horizontal but switched the opposite direction
+ for(x = 0; x < M_IMGDATA->m_width; x++)
+ {
+ sum_r = sum_g = sum_b = sum_a = 0;
+
+ // Calculate the average of all pixels in our blur radius box for the first pixel of the column
+ for(kernel_y = -blurRadius; kernel_y <= blurRadius; kernel_y++)
+ {
+ // To deal with the pixels at the start of a column so it's not grabbing GOK values from memory at negative indices of the image's data or grabbing from the previous column
+ if(kernel_y < 0)
+ pixel_idx = x;
+ else
+ pixel_idx = x + kernel_y * M_IMGDATA->m_width;
+
+ sum_r += src_data[pixel_idx * 3 + 0];
+ sum_g += src_data[pixel_idx * 3 + 1];
+ sum_b += src_data[pixel_idx * 3 + 2];
+ sum_a += src_alpha ? src_alpha[pixel_idx] : 0;
+ }
+ dst_data[x * 3 + 0] = sum_r / (blurRadius * 2 + 1);
+ dst_data[x * 3 + 1] = sum_g / (blurRadius * 2 + 1);
+ dst_data[x * 3 + 2] = sum_b / (blurRadius * 2 + 1);
+ if(src_alpha)
+ dst_alpha[x] = sum_a / (blurRadius * 2 + 1);
+
+ // Now average the values of the rest of the pixels by just moving the box along the column from top to bottom
+ for(y = 1; y < M_IMGDATA->m_height; y++)
+ {
+ // Take care of pixels that would be beyond the top edge by duplicating the top edge pixel for the column
+ if(y - blurRadius - 1 < 0)
+ pixel_idx = x;
+ else
+ pixel_idx = x + (y - blurRadius - 1) * M_IMGDATA->m_width;
+
+ // Subtract the value of the pixel at the top of our blur radius box
+ sum_r -= src_data[pixel_idx * 3 + 0];
+ sum_g -= src_data[pixel_idx * 3 + 1];
+ sum_b -= src_data[pixel_idx * 3 + 2];
+ sum_a -= src_alpha ? src_alpha[pixel_idx] : 0;
+
+ // Take care of the pixels that would be beyond the bottom edge of the image similar to the top edge
+ if(y + blurRadius > M_IMGDATA->m_height - 1)
+ pixel_idx = x + (M_IMGDATA->m_height - 1) * M_IMGDATA->m_width;
+ else
+ pixel_idx = x + (blurRadius + y) * M_IMGDATA->m_width;
+
+ // Add the value of the pixel being added to the end of our box
+ sum_r += src_data[pixel_idx * 3 + 0];
+ sum_g += src_data[pixel_idx * 3 + 1];
+ sum_b += src_data[pixel_idx * 3 + 2];
+ sum_a += src_alpha ? src_alpha[pixel_idx] : 0;
+
+ // Save off the averaged data
+ dst_data[(x + y * M_IMGDATA->m_width) * 3 + 0] = sum_r / (blurRadius * 2 + 1);
+ dst_data[(x + y * M_IMGDATA->m_width) * 3 + 1] = sum_g / (blurRadius * 2 + 1);
+ dst_data[(x + y * M_IMGDATA->m_width) * 3 + 2] = sum_b / (blurRadius * 2 + 1);
+ if(src_alpha)
+ dst_alpha[x + y * M_IMGDATA->m_width] = sum_a / (blurRadius * 2 + 1);
+ }
+ }
+
+ return ret_image;
+}
+
+// The new blur function
+wxImage wxImage::Blur(int blurRadius)
+{
+ wxImage ret_image;
+ ret_image.Create(M_IMGDATA->m_width, M_IMGDATA->m_height, false);
+
+ // Blur the image in each direction
+ ret_image = BlurHorizontal(blurRadius);
+ ret_image = ret_image.BlurVertical(blurRadius);
+
+ return ret_image;
+}
+
projects / wxWidgets.git / commitdiff
